Hoechst-Roussel Pharmaceuticals, Inc. (Hoechst) appeals the decision of the United States District Court for the Eastern District of Virginia, No. 95-CV-650 (October 27, 1995), granting summary judgment to Bruce A. Lehman, the Commissioner of Patents and Trademarks (the Commissioner), that Hoechst is not entitled to extend the term of its United States Patent No. 4,631,286 under 35 U.S.C. § 156 (1994). We affirm on the basis that Hoechst’s patent does not claim either the drug product which received regulatory approval or its use.
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On June 4,1990, Warner-Lambert Company (Warner-Lambert), which is not a party to this case, submitted a new drug application to the Food and Drug Administration (FDA) for approval to market the drug COG-NEX® to treat Alzheimer’s disease. The active ingredient in COGNEX® is tacrine hydrochloride. On September 9, 1993, the FDA granted Warner-Lambert approval to market COGNEX®.
On September 30, 1993, Hoechst sued Warner-Lambert for infringement of its United States Patent No. 4,631,286 (the ’286 patent) which issued on December 23, 1986. The ’286 patent does not claim tacrine hydrochloride; rather, it discloses and claims both the compound 1-hydroxy-tacrine and a method of treating a patient in need of memory enhancement by administering an effective amount of 1-hydroxy-tacrine.1 Tacrine hydrochloride, after ingestion, metabolizes into 1-hydroxy-tacrine and other compounds. On October 5, 1994, the court entered a consent judgment in which Warner-Lambert admitted that tacrine hydrochloride infringes certain claims of the ’286 patent.
While it was litigating against Warner-Lambert, Hoechst also filed with the United States Patent and Trademark Office (PTO) an application for extension of the term of the ’286 patent, pursuant to 35 U.S.C. § 156, based on the regulatory review period for COGNEX®. On April 3, 1995, the Commissioner denied Hoechst’s application for patent term extension. The Commissioner decided that Hoechst was not a proper applicant for term extension because Hoechst was not involved, either directly or indirectly, in the regulatory approval pro*758cess for tacrine hydrochloride. In addition, the Commissioner determined that Hoeehst’s patent term should not be extended because the ’286 patent does not claim tacrine hydrochloride, as required by the statute.
Hoechst appealed the Commissioner’s decision in the district court. After both parties moved for summary judgment, the district court granted the Commissioner’s motion and held that Hoechst was not entitled to a patent term extension. The district court agreed with the Commissioner that Hoechst was not a proper applicant for extension, and that the ’286 patent does not claim tacrine hydrochloride. Hoechst appeals the district court’s decision, which we have jurisdiction to review pursuant to 28 U.S.C. § 1295(a)(1) (1994).
II
Title 35, section 156, entitled “Extension of patent term,” recites, in relevant part:
(a) The term of a patent which claims a product, a method of using a product, or a method of manufacturing a product shall be extended in accordance with this section from the original expiration date of the patent if ...
(4) the product has been subject to a regulatory review period before its commercial marketing or use.
35 U.S.C. § 156(a) (1994) (emphasis added).
The Commissioner contends that Hoechst is not entitled to have the term of the ’286 patent extended because that patent does not “claim” either the product that received FDA approval (tacrine hydrochloride) or a method of using that product. Hoechst responds that a patent “claims” an FDA-approved product, within the meaning of that term as employed in the statute, if the FDA-approved product would infringe a claim of that patent. Because use of tacrine hydrochloride allegedly infringes its claim to a method of using 1-hydroxy-tacrine, Hoechst contends that the ’286 patent “claims” a method of using tacrine hydrochloride.
The district court agreed with the Commissioner’s interpretation of the term “claims” and granted the Commissioner’s motion for summary judgment. We review the district court’s grant of summary judgment to ensure that the standards of Fed. R.Civ.P. 56(c) have been met. Glaxo Operations UK Ltd. v. Quigg, 894 F.2d 392, 395, 13 USPQ2d 1628, 1630 (Fed.Cir.1990). Because the parties do not dispute any issues of fact, we are left with the legal question involving the meaning of the statutory term “claims,” which we decide with independence from the trial court’s interpretation. See Merck & Co. v. Kessler, 80 F.3d 1543, 1549, 38 USPQ2d 1347, 1351 (Fed.Cir.1996).
Ill
We begin our task of statutory interpretation by examining the text of the statute. In so doing, we must interpret statutory words as taking their ordinary, common meaning unless otherwise defined by Congress. Glaxo, 894 F.2d at 395, 13 USPQ2d at 1630.
As explained above, the text of section 156 states in relevant part, “[t]he term of a patent which claims a product, a method of using a product, or a method of manufacturing a product shall be extended.,..” The term “claims” has been used in patent legislation since the Patent Act of 1836 to define the invention that an applicant believes is patentable. See Act of July 4, 1836, ch. 357, § 6, 5 Stat. 117. Since that time, the term has represented that portion of the specification that defines the patent owner’s property rights in the invention. See Corning Glass Works v. Sumitomo Elec. U.S.A., Inc., 868 F.2d 1251, 1257-58, 9 USPQ2d 1962, 1966-67 (Fed.Cir.1989) (“A claim in a patent provides the metes and bounds of the right which the patent confers on the patentee to exclude others from making, using, or selling the protected invention.”). Accordingly, the current patent statutes require that “[t]he specification shall conclude with one or more claims particularly pointing,out and distinctly claiming the subject matter which the applicant regards as his invention.” 35 U.S.C. § 112 (1994). In addition, in order for a patent to “claim” a product, the patentee must have satisfied numerous tests of patent-ability, including, inter alia, disclosure of the *759best mode of making the claimed product, and a description which would enable a person skilled in the art to make and use the claimed invention.2 See id.
This concept of a claim is related to, but distinct from, the concept of infringement. Direct infringement consists of making, using, offering to sell, or selling the invention defined by the claims of a patent, without the authority of the patent owner. See 35 U.S.C. § 271. With respect to direct infringement, then, the claims define the patent owner’s property rights whereas infringement is the act of trespassing upon those rights. The relationship between infringement and the claims becomes even more tenuous under the doctrine of equivalents, where a product is deemed to infringe the patentee’s right to exclude even though the product does not fall within the scope of the patent’s claims. See Wilson Sporting Goods Co. v. David Geoffrey & Assocs., 904 F.2d 677, 684, 14 USPQ2d 1942, 1948 (Fed. Cir.1990). In sum, the concept of a “claim” is different from the concept of infringement, and, as a result, the plain meaning of “claims” is not the same as the plain meaning of infringement.
As applied to the present case, this plain meaning of the term “claims” supports the Commissioner’s argument. In the ’286 patent, Hoechst has not claimed either the active ingredient that received FDA approval, tacrine hydrochloride, or a method of using that ingredient.3 Instead, Hoechst has claimed the chemically distinct product 1-hydroxy-tacrine and the method of using that product. Admittedly, Hoechst may be entitled to exclude others from administering tacrine hydrochloride to patients. But this right to exclude would not arise from the fact that Hoechst has claimed tacrine hydrochloride; nor would it arise from the fact that COGNEX® contains the product claimed by Hoechst, 1-hydroxy-tacrine. Instead, the right to exclude may arise from the fact that when administered, tacrine hydrochloride metabolizes into another product, 1-hy-droxy-tacrine, which Hoechst has claimed.4 See Zenith Labs. v. Bristol-Myers Squibb, 19 F.3d 1418, 1422, 30 USPQ2d 1285, 1288 (Fed. Cir.1994) (infringement may occur if the administered product is converted in vivo into the claimed product). Therefore, we agree with the Commissioner that Hoechst’s ’286 patent does not “claim,” within the ordinary meaning of that term, either the product tacrine hydrochloride or a method of using that product.
IV
Faced with the settled ordinary meaning of the term “claims,” Hoechst argues that Congress did not employ the term with that meaning. Hoechst argues that the legislative history of section 156 instead reveals that Congress intended to include any patent that has claims that are infringed by the making, using, or selling of an FDA-approved product.
“When ... the terms of a statute [are] unambiguous, judicial inquiry is complete, except in rare and exceptional circum*760stances.” Rubin v. United States, 449 U.S. 424, 430, 101 S.Ct. 698, 701, 66 L.Ed.2d 633 (1981). Although the plain meaning of “claims” would appear to resolve the case, we examine the legislative history to ensure that there exists no clearly expressed legislative intention contrary to the statutory language. See Glaxo, 894 F.2d at 395, 13 USPQ2d at 1630-31. Given the existence of a plain meaning, Hoechst “must provide an ‘extraordinary showing of contrary intentions.’ ” See id. (quoting Garcia v. United States, 469 U.S. 70, 75, 105 S.Ct. 479, 482, 83 L.Ed.2d 472 (1984)). We conclude that Hoechst has not made a sufficiently strong showing to warrant a deviation from the term’s plain meaning.
Hoechst relies on two items of legislative history in support of its argument. First, the legislative history states that “[t]he term ‘claims’ was selected because it is the term used in the patent law to describe the invention which the patent owner or its assignee may prevent others from making, using or selling during the seventeen year term of the patent____” H.R.Rep. No. 857, pt. I, 98th Cong., 2d Sess. 37 (1984), reprinted in 1984 U.S.C.C.A.N. 2647, 2670. This segment of legislative history, however, does not contradict the plain meaning of the term “claims,” as defined above. If anything, it supports the notion that the claims define the scope of the property rights in the invention. Moreover, it indicates that Congress deliberately chose the term “claims” because it already had a well-known meaning and usage in the patent law.
The second piece of legislative history that Hoechst relies upon recites that “[t]he policy which the Committee seeks to implement ... is, in brief, that the first patent ... which claims the approved product, in the sense that the approved product would infringe a claim of that patent ... is the patent which should be rewarded with an extension____” H.R.Rep. No. 857 at 38, reprinted in 1984 U.S.C.C.A.N. at 2670. Hoechst contends that this statement makes clear that by employing the term “claims,” Congress intended only that the approved product infringe a claim of the patent.
This portion of the legislative history, indeed, provides some suggestion that Congress may have intended the term “claims” to simply require that the FDA-approved product infringe the patent’s claims. It does not, however, rise to the level of a “clearly expressed legislative intention contrary to the statutory language.” Madison Galleries, Ltd. v. United States, 870 F.2d 627, 629 (Fed.Cir.1989).
Given that Congress employed both the term “claims” and the term “infringement” in this piece of legislative history, we would expect Congress to employ the term “infringement” somewhere in the patent term extension statute if it intended Hoechst’s interpretation. Instead, section 156 consistently employs the term “claim” (or “claims”), see § 156(d)(1)(B) (directing the patent owner to identify “each claim of such patent which claims the approved product or a method of using or manufacturing the approved product” (emphasis added)); § 156(b) (describing the rights granted in terms of the type of claims involved), and there exists a notable absence of any reference to infringement. We must assume that the usage employed by Congress is deliberate, in view of the fact that Congress used the term infringement in other sections of the act. For example, Congress used the term “infringement” in section 271 to define certain acts of infringement, and to excuse other acts of infringement which are conducted solely for the purposes of obtaining FDA approval. See 35 U.S.C. §§ 271(e)(l)-(2).
Moreover, given the distinction between a “claim” and its infringement, had Congress intended the usage urged by Hoechst, it could have drafted section 156(a) to make that intention more clear than appears from the language actually chosen. For example, Congress could have drafted § 156 to recite: “The term of a patent which claims a product, a method of using a product, or a method of manufacturing a product which claim is infringed by an FDA-approved product, use of an FDA-approved product, or manufacture of an FDA-approved product shall be extended____” Such a statute would clearly indicate that the patent need not claim the FDA-approved product or a method of using *761an FDA-approved product; rather, it need only claim a product or method of using that product, so long as that claim is infringed by the FDA-approved product or its use. Congress, however, did not choose to do so. Instead, Congress chose to require that the patent, itself, claim the FDA-approved product or its use. See §§ 156(a), (f)(1)(A), (f)(2)(A).
In sum, because the evidence cited by Hoeehst does not amount to an extraordinary showing that Congress intended the term “claims” to have anything other than its plain meaning, we conclude that the term should be given its ordinary meaning from the patent law.5
V
Hoeehst’s ’286 patent neither claims tacrine hydrochloride nor a method of using that product. Therefore, the district court’s judgment that Hoeehst is not entitled to have the term of the ’286 patent extended is
AFFIRMED.
No costs.
. Tacrine hydrochloride is claimed in United States Patent No. 4,816,456, held by Dr. William Summers. Dr. Summers, an intervenor in this case, also seeks to extend the term of his patent based on the FDA's approval of COGNEX®. Dr. Summers's application for term extension is pending before the Commissioner.
. These same requirements, of course, also apply to process patents.
. The statute defines “product" to include a "drug product," 35 U.S.C. § 156(f)(1), which, in turn, is defined as the active ingredient of a drug that receives FDA approval, 35 U.S.C. § 156(f)(2)(A). For purposes of patent term extension, this active ingredient must be present in the drug product when administered. See Glaxo Operations UK Ltd. v. Quigg, 706 F.Supp. 1224, 1227-28, 10 USPQ2d 1100, 1103 (E.D.Va.1989), aff'd 894 F.2d 392, 13 USPQ2d 1628 (Fed.Cir. 1990). Although the term “product” in the statute includes any salt or ester of the active ingredient of a drug that receives FDA approval, 1-hydroxy-tacrine is neither a salt nor an ester of tacrine hydrochloride.
. Hoechst contends that although it does not claim the product tacrine hydrochloride, it based its application for patent term extension on its claims covering a method of using tacrine hydrochloride. We fail to see how this advances Hoechst’s case. Section 156 allows the Commissioner to extend the term of a patent that claims a method of using an FDA-approved product. In the present case, this would include patents that claim a method of using tacrine hydrochloride. Hoechst’s '286 patent, however, claims a method of using 1-hydroxy-tacrine rather than a method of using tacrine hydrochloride. Ultimately, the problem for Hoechst is the same for both its product and method claims: its patent claims relate to 1-hydroxy-tacrine rather than tacrine hydrochloride.
. The parties also dispute whether Hoeehst is a proper applicant for patent term extension. The Commissioner argues that Hoeehst is not because Hoeehst did not participate in the FDA approval process, either directly or indirectly. Hoeehst contends that the statute requires neither participation by the patentee in the regulatory process, nor any special relationship between the patentee and the party receiving regulatory approval. We do not reach this issue, however, in light of our conclusion that Hoeehst has claimed neither the product receiving FDA approval nor its use.