with whom Justice Brennan and Justice Stevens join, dissenting.
The question in this case is whether the Board of Governors of the Federal Reserve System (Board) adopted an erroneous interpretation of law when it concluded that *161commercial paper is not a “security” under, and hence is not subject to the proscriptions of, §§16 and 21 of the Glass-Steagall Act, 48 Stat. 184, 189, as amended, 12 U. S. C. §§24 Seventh and 378(a)(1). The area of banking law in which this question arises is as specialized and technical as the financial world it governs, and the relevant statutes are far from clear or easy to interpret. The question is accordingly one on which this Court must give substantial deference to the Board’s construction. Because of the Board’s expertise and experience in this complicated area of law, and because of its extensive responsibility for administering the federal banking laws, the Board’s interpretation of the Glass-Steagall Act must be sustained unless it is unreasonable. No. 83-614, Securities Industry Assn. v. Board of Governors of Federal Reserve System, post, at 217, and n. 16; Investment Company Institute v. Camp, 401 U. S. 617, 626-627 (1971); see also Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 844-845 (1984); Board of Governors of Federal Reserve System v. Investment Company Institute, 450 U. S. 46, 56-58 (1981); FEC v. Democratic Senatorial Campaign Committee, 454 U. S. 27, 39 (1981).
Analysis of this ease requires simply an examination of the usual sources of statutory interpretation — primarily the statutory language — to determine whether the Board’s reading is a reasonable one, even if it is not the only reasonable one. The Court of Appeals departed from this approach when it limited its approval of the Board’s position to certain kinds of sales of certain kinds of commercial paper that it thought did not present certain dangers addressed by the Glass-Steagall Act, A. G. Becker Inc. v. Board of Governors of Federal Reserve System, 224 U. S. App. D. C. 21, 36-37, 693 F. 2d 136, 151-152 (1982), and the Solicitor General, though not actually adopting a similarly limited position on behalf of the Board, has devoted a significant portion of his brief in this Court to elaborating the safety analysis underlying the Court of Appeals’ limitation, Brief for Respondents 33-44. It is the Board’s position, however, and not that of the Court of *162Appeals or of the Solicitor General, to which deference is due. It is the Board that has the experience, expertise, and responsibility that require us to give it “considerable deference in its interpretation of the statute.” United States v. Mitchell, 445 U. S. 535, 550 (1980) (White, J., dissenting).1
The Board’s own careful and thorough opinion, I believe, amply demonstrates the reasonableness — perhaps the inevitability — of its construction of the critical statutory language. Moreover, the Court’s construction of the statute and petitioners’ objections to the Board’s position are unpersuasive. In these circumstances, the Court should defer to the Board and uphold its ruling. Because the Court does not do so, I respectfully dissent.
I — I
The language of §§ 16 and 21 of the Glass-Steagall Act makes it clear that, in considering whether the Act prohibits a covered bank2 from selling third-party commercial paper, the threshold issue is whether commercial paper is a “security” within the meaning of those two sections. See Investment Company Institute v. Camp, supra, at 634-635. If it is not, then commercial paper, which is a debt rather than an equity instrument, is not subject to § 16’s regulation of commercial bank transactions in “securities and stock.”3 Nor *163is it subject to §21’s regulation of transactions in “stocks, bonds, debentures, notes, or other securities.” (Emphasis added.)4 Section 21’s use of the word “other” implies that no debt instrument is within the scope of the section unless it is also a “security.”
Despite differences in language, moreover, §§16 and 21 are coextensive in their proscriptions of commercial banks’ securities activities. The two provisions approach the same problem from different directions: broadly speaking, § 16 tells firms that engage in commercial banking that they cannot engage in certain securities activities; §21 tells firms that engage in certain securities activities that they cannot engage in commercial banking. See Board of Governors of Federal Reserve System v. Investment Company Institute, *164450 U. S., at 62-63. Moreover, § 21 itself contains a proviso intended “to make it clear that the prohibition in Section 21 [does] not prohibit banks from conducting those securities activities permitted by Section 16.” 5 V. DiLorenzo, W. Schlichting, T. Rice, & J. Cooper, Banking Law § 96.02[2], p. 96-15 (1981) (footnote omitted). See H. R. Rep. No. 742, 74th Cong., 1st Sess., 16 (1935) (hereinafter H. R. Rep. No. 742); S. Rep. No. 1007, 74th Cong., 1st Sess., 15 (1935) (hereinafter S. Rep. No. 1007).5 Indeed, petitioners concede that §§16 and 21 proscribe the same securities activities by commercial banks. See Brief for Petitioner A. G. Becker Inc. 24; Brief for Petitioner Securities Industry Association 12. For this reason, the language of both provisions must be examined to determine the intended coverage of the Glass-Steagall Act.
It is apparent from the statutory language that there is no “plain meaning” of the key terms in either § 16 or § 21 that forecloses the Board’s interpretation. The Glass-Steagall Act nowhere defines the term “securities,” and the term is not so well defined, either generally or as a legal term of art, that commercial paper is plainly included within its meaning. In particular, nothing on the face of the Glass-Steagall Act reveals whether “securities” refers to the class of all written instruments evidencing a financial interest in a business or, alternatively, to a narrower class of capital-raising investment instruments, as opposed to instruments evidencing short-term loans used to fund current expenses. The term “notes” in §21, on which petitioners rest their argument that the Glass-Steagall Act covers commercial paper, is likewise susceptible to different meanings. Although “note” is often used generically to refer to any written promise to pay a specified sum on demand or at a specified time, see Uniform *165Commercial Code § 3-104, 2 U. L. A. 17 (1977); Black’s Law Dictionary 956 (5th ed. 1979); G. Munn & F. Garcia, Encyclopedia of Banking and Finance 724-725 (8th ed. 1983), it is also used, more narrowly, to refer to a particular kind of capital-raising debt instrument distributed under an indenture agreement, like bonds or debentures but of shorter maturity, see id., at 725 (“The term note also is sometimes applied to short-term bonds . . .”); 1 A. Dewing, The Financial Policy of Corporations 178 (5th ed. 1953).6 Commercial paper, which consists of “prime quality, negotiable, usually unsecured short-term promissory notes issued by business organizations to meet part of their short-term credit needs,” App. to Pet. for Cert. 65a (footnote omitted), does not come within the narrower interpretations of either “securities” or “notes.” Thus, the words “securities” and “notes” in §§16 and 21, considered alone, are susceptible to the Board’s construction.
Not only do the key terms of §§ 16 and 21, read in isolation, admit the Board’s interpretation, but the provisions as a whole lend strong, perhaps decisive, support to the Board’s view. A reading of §§16 and 21 reveals that petitioners’ interpretation, like any other interpretation that treats commercial paper as a “security,” does violence to the statutory language. And the Board’s interpretation makes sense of the statutory language and of its history.
Section 21. Petitioners pin almost their entire statutory-language argument on the contention that § 21 uses the term “notes” in its generic sense, as comprising all written promises to pay a specified sum on demand or at a specified time. Aside from the absence of any affirmative evidence favoring that interpretation, there are several reasons to think that petitioners’ contention about the broad meaning of “notes” is *166erroneous. First, § 21’s mention of bonds and debentures— both of which are written promises to pay a specified sum on demand or on a specified date, see 1 Dewing, supra, at 169, 226 — would be redundant if “notes” were as sweeping in its scope as petitioners suggest. Second, and more important, if § 21 included all written promises to pay a specified sum on demand or at a specified time, it would apply to such instruments as certificates of deposit, notes representing a bank loan to a business, bankers’ acceptances, and loan participa-tions. See Note, 91 Yale L. J. 102, 118-119, and nn. 126-129 (1981). Yet such a construction of “notes” would render unlawful much banking activity that not even petitioners urge is anything but legitimate commercial banking. For example, petitioners’ reading of § 21 would make it “unlawful. . . [f]or any person . . . engaged in the business of issuing, . . . selling, or distributing . . . [certificates of deposit or bankers’ acceptances] ... to engage at the same time to any extent whatever in the business of receiving deposits . . . .” 12 U. S. C. § 378(a)(1).7 In short, petitioners’ reading of § 21 makes nonsense of the statutory language, and it therefore cannot be correct. The Board’s reading, the only alternative to petitioners’, gains considerable support from this conclusion.
Finally, the language of §21 provides affirmative support for the reasonableness of the Board’s position that “notes” refers only to instruments characterizable as short-term bonds or debentures. In No. 83-614, Securities Industry Assn. v. Board of Governors of Federal Reserve System, post, *167p. 207, we rely on the “ ‘familiar principle of statutory construction that words grouped in a list should be given related meaning/ ” to support our conclusion that the Board reasonably construed the term “public sale” in §20 of the Glass-Steagall Act, 12 U. S. C. § 377, “to refer to the underwriting activity described by the terms that surround it.” Post, at 218 (quoting Third National Bank v. Impac, Ltd., 432 U. S. 312, 322 (1977)). The same principle is relevant in this case. That stocks, bonds, and debentures are all instruments purchased for investment purposes suggests that “notes” should be read to refer only to instruments similarly purchased for investment purposes. More specifically, the listing of bonds, debentures, and notes as the three “securities” (as opposed to “stock”) named in § 21 suggests that the ambiguity in “notes” should be resolved, as the Board has done, by reading the term to refer to instruments similar in character to bonds and debentures. In sum, the Board’s position makes good sense of § 21’s list of financial instruments by giving the items in the list related meanings.
Section 16. The language of §16, like that of §21, cannot bear petitioners’ construction. Any reading of §16 that deems, commercial paper a “security” leaves federal banking law laden with contradictions.
Section 16 flatly forbids covered banks to purchase “securities and stock” for their own accounts, but it makes a limited exception for “investment securities.” See n. 3, supra.8 It *168is undisputed that commercial banks may purchase commercial paper for their own accounts.9 Hence, if commercial paper is a “security” within the meaning of § 16, it must be an “investment security.” To put the same point in the reverse order, if commercial paper is not an “investment security,” it cannot be a security covered by §16 at all: otherwise, contrary to what even petitioners acknowledge to be so, banks could not buy it for their own accounts. The Board concluded that commercial paper is not an “investment security,” and therefore is not a “security,” under §16, App. to Pet. for Cert. 69a-74a, and that conclusion is at the very least a reasonable one. Petitioners nowhere dispute the conclusion that commercial paper is not an investment security; indeed, they effectively concede that it is correct. See Tr. of Oral Arg. 7.
The reasons may be briefly summarized. Section 16 defines “investment security” to mean “marketable obligations, evidencing indebtedness of any person, copartnership, asso*169ciation, or corporation in the form of bonds, notes and/or debentures commonly known as investment securities under such further definition of the term ... as may by regulation be prescribed by the Comptroller of the Currency.” 12 U. S. C. §24 Seventh. The Comptroller has never designated commercial paper as an investment security. Moreover, in 1971 the Comptroller’s Chief Counsel took the position that commercial paper does not constitute an investment security. See App. to Pet. for Cert. 73a. In addition, the federal banking regulators, including the Comptroller, have always treated a bank’s purchase of commercial paper as a loan: it must be treated as such in federally required bank reports, and the Comptroller views the statutory limits on loans to individual borrowers, 12 U. S. C. §84, as distinct from § 16’s limits on holding investment securities of a single issuer, 12 CPR §7.1180 (1983). See App. to Pet. for Cert. 72a-73a.
History also supports the Board’s conclusion that commercial paper is not an investment security. The phrase “investment security” originated in the McFadden Act of 1927, 44 Stat. (part 2) 1224, and the Glass-Steagall Act did not purport to alter the meaning of the phrase. The McFadden Act affirmed the authority of national banks to deal in “investment securities,” subject to certain restrictions: it was intended to provide express statutory authorization for national banks’ longstanding practice of dealing in corporate bonds. See H. R. Rep. No. 83, 69th Cong., 1st Sess., 3-4 (1926). Congressman McFadden, the sponsor of the Act, expressly stated during floor debate on the bill that commercial paper had not been and would not be regarded as an “investment security” and hence would be subject to the statutory limitations on loans, not to the restrictions of the McFadden Act. 67 Cong. Rec. 3232 (1926). This statement, which was not disputed by anyone in Congress, accurately reflects the fact that banks’ involvement with commercial paper had long been understood as distinct from their involvement with investment instruments, since the purchase of commercial *170paper was regarded as the making of a short-term loan rather than as an investment.10 Indeed, as the Board pointed out, “historical studies of the commercial paper market. . . indicate that banks purchased and sold commercial paper (and served as commercial paper dealers) pursuant to their lending functions long before commercial banks began expanding their activities into the underwriting of corporate bonds and other debt obligations after the Civil War, activities that were restricted by the McFadden legislation concerning investment securities and, six years later, by the Glass-Steagall Act.” App. to Pet. for Cert. 72a; see id., at 72a, n. 13 (citing, inter alia, Greef, supra n. 9, at 6-7, 15-18, 63, 403-405; Foulke, supra n. 9, at 108). In sum, commercial paper has never been treated, and was not intended to be treated, as an investment security under either the McFadden or the Glass-Steagall Act. Given that banks covered by §16 have the authority to purchase commercial paper for their own accounts, which they could not do if commercial paper were a security under § 16, it follows that commercial paper cannot be a security within the meaning of the Glass-Steagall Act.
Having established that commercial paper is not an “investment security,” it is also possible to draw support for the Board’s conclusion from the original 1933 language of § 16. As enacted in 1933, § 16 prohibited national banks from purchasing “investment securities” for their own account and *171from underwriting any “issue of securities,” but the proviso permitted the purchase of “investment securities” subject to the regulation of the Comptroller of the Currency.11 Thus, the original version of §16 simply does not apply to any instrument, like commercial paper, that is not an investment security. In 1935 Congress altered this language, but it did so simply “to make it clear that national banks and other member banks may purchase and sell stocks for the account of their customers but not for their own accounts.” H. R. Rep. No. 742, p. 18. See also S. Rep. No. 1007, p. 16. Congress had no intent to change the coverage of § 16 with respect to nonequity instruments. In short, the 1933 version of § 16, which was unaltered in any respect relevant to commercial paper, lends strong support to the Board’s position that the Glass-Steagall Act does not apply to commercial paper, which is not an “investment security.”
Indeed, there is good reason to think that Congress understood the term “securities” to mean nothing broader than “investment securities.” First, the 1935 amendment to § 16 substituted “securities and stock” for “investment securities” without suggesting that §16’s application to nonequity instruments was being in any way expanded. Similarly, the *172proviso in § 21, see n. 5, supra, enacted into law in 1935 along with the amendment to §16, refers only to “investment securities” insofar as it addresses banks’ “dealing in, underwriting, purchasing, and selling”; yet it is clear, and it is conceded, that the proviso was intended to make § 21’s prohibitions coextensive with those of §16 with respect to all securities activities. See H. R. Rep. No. 742, p. 16 (amendment makes clear that §21 “does not prohibit any financial institution or private banker from engaging in the securities business to the limited extent permitted to national banks under [§ 16]”); S. Rep. No. 1007, p. 15 (amendment provides that §21 “should not be construed as prohibiting banks, bankers, or financial institutions from engaging in securities activities within the limits expressly permitted in the case of national banks under [§ 16]”). Moreover, § 5(c) of the Glass-Steagall Act likewise refers only to “investment securities and stock”;12 yet that provision, as petitioners concede, makes §16 of the Glass-Steagall Act applicable in full to “state member banks” like the Bankers Trust Company, see Brief for Petitioner A. G. Becker Inc. 2, n. 2; Brief for Petitioner Securities Industry Association 3, n. 3. All of these congressional enactments presuppose that Congress understood “securities” and “investment securities” to refer to the same class of debt instruments, a class that excludes commercial paper.
This conclusion confirms the Board’s view that §§ 16 and 21, as amended in 1935, were intended to apply only to investment instruments akin to stocks, bonds, and debentures. It also comports with what the legislative history reveals to have been of concern to the Congress that enacted Glass-Steagall. During the extensive legislative hearings and *173debates leading up to the enactment of the Glass-Steagall Act, Congress focused its attention on commercial banks’ participation in the markets for long-term and speculative securities, and commercial paper was distinguished from the investment securities that Congress was worried about. See S. Rep. No. 77, supra n. 8, at 4, 8, 9; 75 Cong. Rec. 9904, 9909, 9910, 9912 (1932).13 Moreover, although commercial banks’ purchasing activities were a major subject of congressional concern, and although commercial banks were the dominant buyers of commercial paper at the time, no one in Congress, as far as anything brought to this Court’s attention shows, ever adverted to banks’ commercial paper activities as contributing to the difficulties at which the Act was aimed. See App. to Pet. for Cert. 75a-76a. Thus, the legislative history shows Congress to have been concerned with commercial banks’ involvement with investment instruments, as the Board contends, and not with their involvement with commercial paper.
In sum, the language of §§ 16 and 21 strongly supports the Board’s interpretation. Indeed, petitioners have suggested no other construction that can be accommodated by the language of the statute. Since the legislative history makes it impossible to argue that Congress intended something contrary to the statutory language, the Board’s conclusion about legislative intent concerning commercial paper appears to be compelled by statute. In any event, it is certainly “a reasonable construction of the statutory language and is consistent with legislative intent.” No. 83-614, Securities Industry Assn. v. Board of Governors of Federal Reserve System, post, at 217.
*174II
Petitioners advance several arguments in an effort to demonstrate the error of the Board's reading of the Glass-Steagall Act, but these arguments are unavailing. It is worth noting at the outset that I have no quarrel with the Court’s extensive discussion of the general policies behind the Glass-Steagall Act. Ante, at 144-148. None of that discussion, however, speaks to the threshold question whether commercial paper is among the “securities” to which Congress thought those policies would apply when it adopted the Act. For all of the reasons given above, the Board’s negative answer to that question is all but mandated by the statutory language and is not contradicted by anything in the legislative history. The Board came to the reasonable conclusion that Congress simply had no intention to apply its policies to commercial paper.
Petitioners argue that Congress understood commercial paper to be a “security” in enacting the Securities Act of 1933, 48 Stat. 74, as amended, 15 U. S. C. §77a et seq., the Securities Exchange Act of 1934, 48 Stat. 881, as amended, 15 U. S. C. § 78a et seq. (containing an express exclusion of commercial paper from the definition of “security,” 48 Stat. 882, as amended, 15 U. S. C. § 78c(a)(10)), and the Public Utility Holding Company Act of 1935, 49 Stat. 803, as amended, 15 U. S. C. § 79a et seq. They suggest that this contemporaneous congressional understanding of the scope of the term “securities” requires commercial paper to be treated as a “security” within the meaning of the Glass-Steagall Act. Even accepting its premise, however, the argument does not affect the merits of the Board’s position.
In determining the meaning of a term in a particular statute, the meaning of the term in other statutes is at best only one factor to consider, and it may turn out to be utterly irrelevant in particular cases. Congress need not, and frequently does not, use the same term to mean precisely the same thing in two different statutes, even when the statutes *175are enacted at about the same time. In this case, the argument from other statutes has little or no weight. Petitioners, who make this argument entirely in the abstract, offer no reason to think that Congress specifically intended “security” to have the same meaning in the Glass-Steagall Act and the securities laws, and the first part of this opinion shows that there are many reasons to think otherwise. In addition, the securities laws’ definitions of “security” include some instruments that plainly do not constitute securities under the Glass-Steagall Act. For example, bankers’ acceptances are securities under §2(1) of the Securities Act of 1933, 48 Stat. 74, as amended, 15 U. S. C. § 77b(1), yet commercial banks have long bought and sold and dealt in bankers’ acceptances as a proper part of their commercial banking, the Board having determined in 1934 that bankers’ acceptances were not securities under the Glass-Steagall Act. See App. to Pet. for Cert. 81a.14
That the term “securities” should have different meanings in the different statutes makes good sense. The purposes of the banking and securities laws are quite different. The Glass-Steagall Act was designed to protect banks and their depositors. See Board of Governors of Federal Reserve System v. Investment Company Institute, 450 U. S., at 61; 75 Cong. Rec. 9913-9914 (1932) (remarks of Sen. Bulkley). The securities laws were designed more generally to protect investors and the general public. See United Housing Foundation, Inc. v. Forman, 421 U. S. 837, 849 (1975).
In response to the demonstration that the language of §§ 16 and 21 simply cannot, accommodate their view without outlawing concededly lawful commercial bank activities, petitioners argue that at least some of the activities at issue are authorized by other statutory language. Most important, *176petitioners observe, national commercial banks have been authorized to purchase commercial paper on their own accounts, under their authority to discount and negotiate promissory notes, since enactment of the National Bank Act in 1864, 13 Stat. 101, currently codified in 12 U. S. C. §24 Seventh, immediately prior to § 16 of the Glass-Steagall Act. Thus, a national bank has the power “[t]o exercise by its board of directors or duly authorized officers or agents, subject to law, all such incidental powers as shall be necessary to carry on the business of banking; by discounting and negotiating promissory notes, drafts, bills of exchange, and other evidences of debt; by receiving deposits; by buying and selling exchange, coin, and bullion; by loaning money on personal security; and by obtaining, issuing, and circulating notes according to the provisions of this chapter.”
The existence of separate statutory authorizations for banking activity prohibited by petitioners’ reading of the Glass-Steagall Act, however, only reinforces the Board’s conclusion that “notes” and “securities” cannot have the broad meaning in §§16 and 21 that petitioners attribute to it. If any such statutory authorizations and the proscriptions of the Glass-Steagall Act are both to remain in force, only two conclusions are possible. Either the terms “notes” and “securities” must have a meaning narrower than the generic one; or there is a conflict of statutes that cannot be resolved by any interpretation of the statutory language, so that one part of federal banking law must be read as implicitly repealing or overriding another. The latter alternative is a last resort, however, and must be avoided where an interpretation of the statutory language is available that is consistent with legislative intent and that shows the conflict to be merely apparent and not real. As shown above, the Board’s reading of §§ 16 and 21 is such an interpretation. It makes sense of the language of federal banking law: for example, it construes “notes” in §21, in accordance with the terms that surround it in the statute, as referring to investment instruments and hence as not including commercial paper; at the same time, it *177construes “promissory notes” in the “discounting and negotiating” language of the National Bank Act, in accordance with the terms that surround it in the statute, as referring to commercial banking instruments and hence as including commercial paper. Petitioners and the Court, by contrast, have not suggested any way out of the flat contradictions that their view of the Glass-Steagall Act creates in federal banking law. It was reasonable for the Board to conclude, App. to Pet. for Cert. 74a-75a, that the language of §§ 16 and 21 itself makes untenable the broad reading of “notes” and “securities” that petitioners suggest and should be read in the narrow fashion set out in the Board’s opinion.
Petitioners also contend that the Board’s position is shown to be erroneous by the fact that almost 50 years elapsed between the enactment of the Glass-Steagall Act and the Board’s ruling. This fact, of course, does not undermine— it does not even address — the otherwise unanswered arguments in support of the Board. In any event, it is of little significance. This is not a case in which a contemporaneous agency construction is later abandoned by the agency. Until it ruled in the Bankers’ Trust matter, the Board never took a position on the applicability of the Glass-Steagall Act to commercial paper. That the Board was not asked for almost 50 years to take a position on this question, moreover, simply cannot count for much. There might be any number of reasons — for example, economic reasons (comparative unattractiveness of selling commercial paper) or sociological reasons (conservativism of commercial banks) — to account for commercial banks’ not having sought to sell commercial paper until the late 1970’s. /This Court is in no position to conclude that there simply could be no explanation for this long silence other than the clarity of the Glass-Steagall Act’s prohibition, especially when neither statutory language nor legislative history supports such a conclusion.
In response to the Board’s contention that the language of § 21 is reasonably construed to apply only to instruments with the characteristics of an investment, petitioners argue that *178there is no single set of such characteristics that are common features of stocks, bonds, and debentures, the items listed in §21 that the Board takes as the starting point for its interpretation. This argument, however, mistakenly places “stocks,” on the one hand, and “bonds” and “debentures,” on the other, into a single class. Section 16's reference to “securities and stock” establishes that the Glass-Steagall Act distinguishes two classes — “securities,” which includes only (though not necessarily all) debt instruments, such as bonds and debentures; and “stock,” which includes only equity instruments. The Board’s interpretation of “notes” accordingly need assimilate the term only to the class that includes bonds and debentures, not the class that consists of stock, in order to justify reliance on the canon of statutory construction that words placed together should be given a related meaning. See supra, at 166-167. The Board’s interpretation, which reads “notes” as referring to short-term debt instruments, like bonds and debentures, issued under indenture agreements, does just that.
The Court decries the Board's approach as transforming the Glass-Steagall Act from the prohibitory statute that Congress enacted into a quite different statute delegating regulatory authority over the area to the Board. To be sure, the Board takes the position that the distinguishing characteristic of the instruments covered by the Glass-Steagall Act is whether the instruments represent investment transactions rather than bank-loan transactions. An investment instrument, according to the Board, may be distinguished by reference to a cluster of related characteristics not possessed by commercial paper — for example, the absence of a short maturity, the existence of a substantial secondary market for them, their bearing of “market” risk in addition to “credit” risk, the issuer’s freedom to use the proceeds for fixed capital purposes, their common availability to purchasers in small denominations, and their commonly being bought by a large number of purchasers.
*179There is nothing the least bit unusual about the “cluster” approach to defining a legal term or concept. That is precisely the approach taken by the law every time it gives definition to a term by specifying a set of “factors” to be considered rather than a set of necessary and sufficient conditions to be checked off. The law is replete with instances of this approach, made necessary by the intrinsic complexity and untidiness of our legal concepts and of the world to which they are designed to apply. This approach is hardly out of place in the law’s attempt to describe and regulate the financial world, with all its intricacies and its bewildering variety of nominally different but substantively similar (if not identical) financial instruments and transactions.
There is simply no escaping some kind of functional analysis to separate the commercial and investment banking worlds in particular cases, which petitioners acknowledge is at least one chief aim of the Glass-Steagall Act. As noted above, see supra, at 165-169, the language of §§ 16 and 21 cannot be read in the sweeping fashion suggested by petitioners: otherwise, those provisions would prohibit concededly permitted commercial bank involvement with a variety of instruments such as commercial paper. Petitioners have suggested no way to make the distinctions needed to give sense to the statutory language that does not involve a functional analysis of what constitutes investment banking and what constitutes commercial banking. For example, petitioners have suggested no way to distinguish the “discounting and negotiating” of “promissory notes,” permitted by the National Bank Act, from the “purchasing” of “notes,” prohibited by §§16 and 21 of the Glass-Steagall Act, a distinction that their position requires them to make. It is hard to imagine how that distinction might be drawn without using a “functional” approach to defining the difference between the commercial and investment banking worlds.
Finally, contrary to petitioners’ allegation, the Board’s functional analysis does not vest the Board with a substantial *180amount of regulatory discretion. In particular, it does not permit the Board to make case-by-case judgments about the Glass-Steagall Act’s application to a particular instrument based on the instrument’s safety and on whether it presents the dangers addressed by the Act. Indeed, the Board specifically declined to conduct a policy analysis of whether certain commercial paper activities presented the dangers at which the Act was aimed. See App. to Pet. for Cert. 83a. The Board, unlike the Court of Appeals, concluded that the Glass-Steagall Act is inapplicable to all commercial paper, not just to the particular kinds of commercial paper sold by Bankers Trust, ibid. The Board’s conclusion about the meaning of the Glass-Steagall Act was simply a construction of the statute; it was only under distinct statutory authority to restrain unsafe or unsound banking practices, 38 Stat. 259, 261, as amended, 12 U. S. C. §§ 248 and 321; 64 Stat. 879, as amended, 12 U. S. C. § 1818(b), that the Board issued its guidelines specifying the kinds of commercial paper sales by commercial banks that it would permit.
The Board employed its functional analysis as one small part of its inquiry into the best construction of the statute. The Board did not purport in its ruling to lay down rules for determining what other instruments have the characteristics of an investment instrument so as to constitute a “security” under the Glass-Steagall Act. It simply reasoned that the language and history of the Act demonstrated that the Act does not cover commercial paper. Critical to the Board’s conclusion is the fact that federal banking law treats commercial paper in such a way as to give rise to a flat contradiction if the Glass-Steagall Act were interpreted to embrace it. Because of its characteristics, commercial paper has long been treated, by federal law and by bankers, not as an investment instrument but as an instrument that commercial banks may purchase without regard to the proscriptions of the Glass-Steagall Act. Thus, the Board’s placing of commercial paper in the commercial rather than investment banking *181world is firmly rooted in the statutory language and in a longstanding practice whose lawfulness is not even subject to dispute. Nothing in the Board’s ruling extends to any instrument not already widely and lawfully purchased by commercial banks, and petitioners have not identified any class of financial instruments other than commercial paper that would come within the Board’s reasoning in this case. The Board’s ruling, in other words, is a narrow one with few implications for other applications of the Glass-Steagall Act.
h — I i — i l — I
The dangers that Congress sought to eliminate when it enacted the Glass-Steagall Act are easily stated at a level of generality that might make the Board’s ruling appear inconsistent with congressional policies. The translation of policy into legislation, however, is always complicated by the necessity of taking into account potentially competing and overlapping laws and policies. The task of this Court, therefore, is to interpret the statutory language that Congress enacted into law. Careful attention to the statutory language is especially important in an area as technical and complex as banking law, where the policies actually enacted into law are likely to be complicated and difficult for a nonspecialist judiciary to discern in their proper perspective.
In this case, the statutory language strongly supports the construction adopted by the Board, and it cannot bear the only construction proposed by petitioners and adopted by the Court. The Board’s construction is also wholly consistent with the legislative history. It is singularly inappropriate for this Court, reasoning from the general policies it finds in the statute and with little regard for the statutory language, to reject the construction of the statute adopted by the Board after careful consideration and with full explanation. It is the Board, and not this Court, that has both responsibility for the oversight of much of our Nation’s banking system and expertise and experience in applying the arcane body of law *182that governs it. When the statutory support for the Board’s position is as strong as it is in this case, the Court’s rejection of the agency’s position is unjustified.
I would uphold the Board’s ruling that commercial paper does not constitute a “security” within the meaning of the Glass-Steagall Act. Because the Court of Appeals’ opinion does not squarely uphold the Board’s statutory construction, I would affirm only the judgment of the Court of Appeals, which reverses the District Court’s judgment declaring the Board’s ruling unlawful.
I respectfully dissent.
As petitioner A. G. Becker Inc. says, “[i]t is the Board’s position in its ruling, of course, and not the post-hoc rationalization of its counsel, by which the Board’s conduct must be judged.” Reply Brief for Petitioner A. G. Becker Inc. 3, n. 5. See also id., at 11, n. 23.
All parties acknowledge that banks chartered under state law that are members of the Federal Reserve System, such as Bankers Trust Company, are covered by the Glass-Steagall Act by virtue of 48 Stat. 165, 12 U. S. C. § 335. See n. 12, infra.
Section 16 of the Glass-Steagall Act reads, in relevant part:
“The business of dealing in securities and stock by [a national bank] shall be limited to purchasing and selling such securities and stock without recourse, solely upon the order, and for the account of, customers, and in no case for its own account, and the [national bank] shall not underwrite any *163issue of securities or stock: Provided, That the [national bank] may purchase for its own account investment securities under such limitations and restrictions as the Comptroller of the Currency may by regulation prescribe. ... As used in this section the term ‘investment securities’ shall mean marketable obligations evidencing indebtedness of any person, copartnership, association, or corporation in the form of bonds, notes and/or debentures commonly known as investment securities under such further definition of the term ‘investment securities’ as may by regulation be prescribed by the Comptroller of the Currency.” 12 U. S. C. §24 Seventh.
Section 21 of the Glass-Steagall Act reads, in relevant part:
“[I]t shall be unlawful. . . [f]or any person, firm, corporation, association, business trust, or other similar organization, engaged in the business of issuing, underwriting, selling, or distributing, at wholesale or retail, or through syndicate participation, stocks, bonds, debentures, notes, or other securities, to engage at the same time to any extent whatever in the business of receiving deposits subject to check or to repayment upon presentation of a passbook, certificate of deposit, or other evidence of debt, or upon request of the depositor: Provided, That the provisions of this paragraph shall not prohibit national banks or State banks or trust companies (whether or not members of the Federal Reserve System) or other financial institutions or private bankers from dealing in, underwriting, purchasing, and selling investment securities, or issuing securities, to the extent permitted to national banking associations by the provisions of [§ 16].” 12 U. S. C. § 378(a)(1).
Section 21 states that its provisions “shall not prohibit national banks or State banks . . . from dealing in, underwriting, purchasing, and selling investment securities, or issuing securities, to the extent permitted” by §16. 12 U. S. C. § 378(a)(1).
The 1934 edition of Dewing’s classic work, contemporaneous with the 1933 Glass-Steagall Act, contains the same reference to short-term bonds as “notes.” A. Dewing, The Financial Policy of Corporations 75 (3d rev. ed. 1934). See also H. Moulton, The Financial Organization of Society 111-118 (2d ed. 1925); E. Mead, Corporation Finance 301 (rev. ed. 1919).
Petitioners conceded at oral argument that certificates of deposit, for example, were notes in the generic sense of that term. See Tr. of Oral' Arg. 14. The technical definition of “note” in the Uniform Commercial Code distinguishes certificates of deposit, but it does so only to define a specific class of bank-issued promises to pay money, not because a certificate of deposit is not otherwise a written promise to pay a specified sum on demand or on a specified date. See Uniform Commercial Code § 8-104, 2 U. L. A. 17 (1977).
The Court suggests that § 16’s reference to the “business of dealing in securities and stock” means that § 16 does not flatly prohibit covered banks from purchasing securities and stock for their own accounts, except as authorized by the proviso, but only from the “business of dealing” in them. Ante, at 158-159. Not even petitioners, however, dispute the proposition that §16 constitutes a flat ban on purchasing, subject to the proviso. Indeed, the legislative history makes clear that Congress so intended §16. In particular, stock, which is not subject to the proviso, simply may not be purchased by commercial banks for their own accounts. See S. Rep. No. 77, 73d Cong., 1st Sess., 16 (1933); S. Rep. No. 1007, *168p. 17; H. R. Rep. No. 742, p. 18; 5 V. DiLorenzo, W. Schlichting, T. Rice, & J. Cooper, Banking Law §96.02[2], p. 96-16 (1981).
The Court also treats the purchasing and underwriting prohibitions in the Act as if they were entirely separate. See ante, at 158-159. That treatment is inconsistent with the statutory language. There is no escaping the fact that any “security” that the Act forbids a commercial bank to underwrite the Act also forbids the bank to purchase, unless it is an investment security. Although the purposes of the prohibitions are somewhat different, the link between the prohibitions, at least as far as this case is concerned, is indissoluble.
Indeed, the Board observed that commercial banks have long purchased commercial paper for their own accounts. See App. to Pet. for Cert. 74a, n. 17. See also A. Greef, The Commercial Paper House in the United States 95-96 (1938); R. Foulke, The Commercial Paper Market 65-74 (1931). No one in this litigation or anywhere else has ever suggested that commercial banks do not “purchase” commercial paper. Indeed, not only do the Board and the standard histories of commercial paper refer to banks’ “purchasing” of commercial paper, see, e. g., App. to Pet. for Cert. 74a, n. 17; Greef, supra, at 292-325, 335-346; Foulke, supra, at 65-98, but so too do petitioners, see Brief for Petitioner A. G. Becker Inc. 39; Brief for Petitioner Securities Industry Association 28; Reply Brief for Petitioner Securities Industry Association 3.
In order for commercial paper to be eligible for discount at Federal Reserve banks, its proceeds may not “be used for permanent or fixed investments of any kind, such as land, buildings, or machinery, or for any other fixed capital purpose” or “for transactions of a purely speculative character” or “for . . . trading in . . . investment securities except direct obligations of the United States.” Consistent with the short maturity of commercial paper, the proceeds must be used “in producing, purchasing, carrying, or marketing goods,” “meeting current operating expenses,” or “carrying or trading in direct obligations of the United States.” G. Munn & F. Garcia, Encyclopedia of Banking and Finance 196 (8th ed. 1983).
Section 16 of the Glass-Steagall Act as enacted in 1933 reads, in relevant part:
“The business of dealing in investment securities by the [bank] shall be limited to purchasing and selling such securities without recourse, solely upon the order, and for the account of, customers, and in no case for its own account, and the [bank] shall not underwrite any issue of securities; Provided, That the [bank] may purchase for its own account investment securities under such limitations and restrictions as the Comptroller of the Currency may by regulation prescribe.... As used in this section the term ‘investment securities’ shall mean marketable obligations evidencing indebtedness of any person, copartnership, association, or corporation in the form of bonds, notes and/or. debentures commonly known as investment securities under such further definition of the term ‘investment securities’ as may by regulation be prescribed by the Comptroller of the Currency.” 48 Stat. 184.
Section 5(c) of the Glass-Steagall Act provides:
“State member banks shall be subject to the same limitations and conditions with respect to the purchasing, selling, underwriting, and holding of investment securities and stock as are applicable in the case of national banks under [§ 16].” 48 Stat. 165, 12 U. S. C. § 335.
See also Operation of the National and Federal Reserve Banking Systems: Hearings on S. 4115 before the Senate Committee on Banking and Currency, 72d Cong., 1st Sess., pt. 1, pp. 66-67, 146 (1932); Operation of the National and Federal Reserve Banking Systems: Hearings pursuant to S. Res. 71 before a Subcommittee of the Senate Committee on Banking and Currency, 71st Cong., 3d Sess., App., pt. 7, pp. 1006-1019 (1931).
The Board observed in its ruling under review in this case that similar problems might arise with respect to certificates of deposit, passbook savings accounts, loan participations, and bills of exchange. App. to Pet. for Cert. 81a-82a.