[¶ 1] A. Michelle Cobb appeals from a judgment entered in the Superior Court (Cumberland County, Crowley, J.) affirming the decision of the Board of Counseling Professionals Licensure to discipline her for diagnosing and treating mental health disorders in violation of 32 M.R.S. § 13858 (2005). Cobb, who is a licensed professional counselor (LPC), contends that 32 M.R.S. § 13858 does not prohibit her from diagnosing and treating mental health disorders and that the Board’s interpretation of the statute is arbitrary and capricious. She also contends that because the Board construed the statute in a disciplinary adjudication instead of a rulemaking proceeding, it violated the rulemaking provisions of the Administrative Procedure Act (APA). 5 M.R.S. § 8052 (2005). She further argues that her rights under the Due Process Clauses of the United States and Maine Constitutions were violated because 32 M.R.S. § 13858 is void for vagueness. We affirm the Superior Court’s affirmance of the Board’s decision.
I. BACKGROUND
[¶ 2] The statutory scheme regulating professional counselors describes three types of counselors in addition to the LPC: (1) licensed clinical professional counselor (LCPC); (2) marriage and family therapist; and (3) pastoral counselor.1 32 M.R.S. §§ 13851(2), (7), (7-A), (9), 13858(1) to (3-A) (2005). Cobb has held the LPC license since 1993.
[¶ 3] In 2001, the parents of two children Cobb was counseling filed a complaint against her with the Board. The Board charged Cobb with operating beyond the scope of her license. Specifically, it alleged that she had diagnosed and treated *274mental health disorders, which was beyond the scope of her LPC license.
[¶ 4] Prior to the Board hearing in 2002, the parties signed a stipulation of facts, in which Cobb admitted that “[d]uring the course of professional treatment [she] rendered diagnoses” of the two children and submitted insurance reimbursement forms with the diagnoses. The parties agreed that the preliminary issue for decision by the Board was whether an LPC is authorized to diagnose and treat mental health disorders. The Board interpreted 32 M.R.S. § 13858 as prohibiting LPCs from diagnosing and treating mental health disorders. The pertinent language of section 13858 is: “The license categories ‘licensed clinical professional counselor,’ ‘licensed pastoral counselor’ and ‘licensed marriage and family therapist’ are of equivalent clinical status. Clinical status grants the ability to diagnose and treat mental health disorders.”
[¶ 5] The Board found that Cobb violated this prohibition by diagnosing and treating the two children. It censured Cobb; imposed a fine of $500 and costs of $500; and ordered her to receive thirty hours of supervision.
[¶ 6] Cobb appealed to the Superior Court, which pointed out that the parties’ stipulation did not state that Cobb had diagnosed “mental health disorders,” and found that the Board had erred in not allowing evidence as to the definition of that phrase. The court held that the Board’s interpretation of section 13858 was correct and that an LPC does not have the authority to diagnose and treat mental health disorders. . It further disagreed with Cobb’s contention that the Board had engaged in unlawful rulemaking. The court remanded the matter for the Board to take additional evidence on the meaning of “mental health disorders” as it is used in section 13858 and to determine whether Cobb had diagnosed “mental health disorders.”
[¶ 7] On remand, the Board heard expert testimony on the meaning of “mental health disorders.” It concluded that conditions deemed “mental health disorders” in the Diagnostic and Statistical Manual of Mental Disorders (4th ed.) (DSM-IV) constitute “mental health disorders” for purposes of section 13858. The Board further found that Cobb had, in fact, diagnosed mental health disorders when she filled out the insurance reimbursement forms for the two children. On the forms, under the heading “Diagnosis,” Cobb used codes from the DSM-IV for “Oppositional Defiant Disorder” and “Adjustment Disorder with Disturbance of Conduct.” The Board found that these are mental health disorders in the DSM-IV, and it further found that these same diagnostic terms were in Cobb’s treatment notes. It concluded that Cobb had diagnosed and treated the two children for mental health disorders. The Board reinstated its earlier censure, fine, and supervision order, but it increased the amount of costs to one-half of the actual costs, not to exceed $1500.
[¶ 8] Cobb appealed again to the Superi- or Court, arguing that (1) the Board’s interpretation of section 13858 was arbitrary and capricious; (2) it violated the rulemak-ing procedures of the APA; (3) it was estopped from prosecuting her because its own actions had induced her to act and she had relied upon those actions; (4) section 13858 is unconstitutionally vague; (5) the imposition of costs was arbitrary and capricious; and (6) she was entitled to attorney fees. The court affirmed the Board’s decision.
II. DISCUSSION
[¶ 9] Cobb has not pursued, on appeal to this Court, all of the arguments she urged *275in the Superior Court. She has narrowed the issues to three: (1) whether the Board’s interpretation of section 13858 is arbitrary and capricious; (2) whether its prosecution of her for violating section 13858 is unlawful because it had not promulgated rules interpreting the statute; and (3) whether her rights to due process have been violated because section 13858 is void for vagueness.2
A. Standard of Review
[¶ 10] Because the Superior Court was acting in an appellate capacity, we review the decision of the Board directly. See Munjoy Sporting & Athletic Club v. Dow, 2000 ME 141, ¶ 6, 755 A.2d 531, 536. ‘“The standard of review is limited to whether the [governmental agency] abused its discretion, committed an error of law, or made findings not supported by substantial evidence in the record.’ ” Id. (quoting Davric Me. Corp. v. Me. Harness Racing Comm’n, 1999 ME 99, ¶7, 732 A.2d 289, 293). We will vacate
the decision [only] if the administrative findings, inferences, conclusions or decisions are:
(1) In violation of constitutional or statutory provisions;
(2) In excess of the statutory authority of the agency;
(3) Made upon unlawful procedure;
(4) Affected by bias or error of law;
(5) Unsupported by substantial evidence on the whole record; or
(6) Arbitrary or capricious or characterized by abuse of discretion.
5 M.R.S. § 11007(4)(C) (2005).
[¶ 11] Regarding the first issue raised in this appeal, which is the interpretation of section 13858, the cardinal rule of statutory interpretation is to give effect to the intention of the Legislature. We discern legislative intent from the plain meaning of the statute and the context of the statutory scheme. Brent Leasing Co., Inc. v. State Tax Assessor, 2001 ME 90, ¶ 6, 773 A.2d 457, 459. All words in a statute are to be given meaning, and none are to be treated as surplusage if they can be reasonably construed. Stromberg-Carlson Corp. v. State Tax Assessor, 2001 ME 11, ¶ 9, 765 A.2d 566, 569.
[¶ 12] The statutory construction statute provides: “Technical words and phrases and such as have a peculiar meaning convey such technical or peculiar meaning.” 1 M.R.S. § 72(3) (2005). “In construing a statute, technical or trade expressions should be given a meaning understood by the trade or profession.” State v. Vogl, 149 Me. 99, 109, 99 A.2d 66, 70 (1953).
[¶ 13] When a case concerns the interpretation of a statute that an administrative agency administers and that is within its area of expertise, our scope of review is to determine first whether the statute is ambiguous. Competitive Energy Seros. LLC v. Pub. Utils. Comm’n, 2003 ME 12, ¶ 15, 818 A.2d 1039, 1046. If the statute is unambiguous, we do not defer to the agency’s construction, but we interpret the statute according to its plain language. Id. If the statute is ambiguous, we defer to the agency’s interpretation, and we affirm the agency’s interpretation unless it is unreasonable. Id. This is the same two-step analysis developed by the United States Supreme Court in Chevron U.S.A Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837, 842-43, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). The Court described the function of a court in the first step as follows: “If a court, employing traditional tools of statutory construction, ascertains *276that Congress had an intention on the precise question at issue, that intention is the law and must be given effect.” Id. at 843 n. 9.
B. The Board’s Interpretation of Section 13858
[¶ 14] The first issue is whether 32 M.R.S. § 13858 is ambiguous regarding the authority of LPCs to diagnose and treat mental health disorders. The Board interpreted section 13858 to mean that LPCs are not authorized to diagnose and treat mental health disorders. Section 13858 describes which licensees have clinical status and states that “[cjlinical status grants the ability to diagnose and treat mental health disorders.” The salient question is whether the statute unambiguously reflects a legislative intention that licensees who do not have clinical status are without the authorization to diagnose and treat mental health disorders.
[¶ 15] The plain language of section 13858 grants clinical status to three of the four categories of licensed counselors, and it provides that licensees with clinical status have the authority to diagnose and treat mental health disorders: “The license categories ‘licensed clinical professional counselor,’ ‘licensed pastoral counselor’ and ‘licensed marriage and family therapist’ are of equivalent clinical status. Clinical status grants the ability to diagnose and treat mental health disorders.” 32 M.R.S. § 13858.
[¶ 16] Section 13858 plainly does not give clinical status to the category of LPC. Nowhere do the licensing statutes grant LPCs clinical status or otherwise give LPCs the authority to diagnose and treat mental health disorders. The statute plainly and unambiguously denies clinical status to LPCs, and because it only authorizes licensees with clinical status to diagnose and treat mental health disorders, LPCs do not have the authority to do so.
[¶ 17] The text of the statutory scheme reinforces this interpretation. The definitional statute gives LPCs the authority to render services to “assist” their clients “in achieving more effective personal, emotional, social, educational and vocational development and adjustment.” 32 M.R.S. § 13851(9). This is in contrast to LCPCs, who have the authority “to assess and treat intrapersonal and interpersonal problems and other dysfunctional behaviors.” 32 M.R.S. § 13851(2). LPCs, LCPCs, and pastoral counselors apply the principles and procedures of counseling, 32 M.R.S. § 13851(2), (7-A), (9), which procedures are defined in 32 M.R.S. § 13851(8):
8. Procedures of counseling. “Procedures of counseling” means methods and techniques that include, but are not limited to, the following.
A. “Assessment” means selecting, administering and interpreting instruments designed to assess personal, interpersonal and group characteristics.
B. “Consulting” means the application of scientific principles and procedures in counseling to provide assistance in understanding and solving a current or potential problem that the client may have in relation to a 3rd party, be it an individual, a family, a group or an organization.
C. “Counseling” means assisting individuals, families or groups through the counseling relationship to develop understanding of intrapersonal and interpersonal problems, to define goals, to make decisions, to plan a course of action reflecting their needs, and to use information and community resources, as these procedures are related to personal, social, educational and vocational development.
*277D. “Referral” means the evaluation of information to identify needs or problems of the counselee and to determine the advisability of referral to other specialists, informing the coun-selee of that judgment, and communicating as requested or deemed appropriate with referral sources.
[¶ 18] These procedures involve “assessment,” which in turn is defined to mean “selecting, administering and interpreting instruments designed to assess personal, interpersonal and group characteristics.” 32 M.R.S. § 13851(8)(A). Although application of the procedures of counseling give LPCs, such as Cobb, the authority to perform assessments, LPCs are not granted the same authority to “assess and treat intrapersonal and interpersonal problems and other dysfunctional behavior” that LCPCs and pastoral counselors are given. Compare 32 M.R.S. § 13851(2), (7-A), with 32 M.R.S. § 13851(8)(A), (9).
[¶ 19] The requirements for licensure differ for the four categories of licenses. Among the many requirements, three of the license categories are required to have clinical training. LCPCs are required to have a minimum of 3000 hours of supervised clinical experience, 32 M.R.S. § 13858(2)(B); marriage and family therapists are required to have a one-year clinical practicum as well as 1000 hours of direct clinical contact, 32 M.R.S. § 13858(3); and pastoral counselors are required to have 400 hours of clinical pastoral education, 32 M.R.S. § 13858(3-A)(B). These are the three license categories that are granted clinical status in section 13858. In contrast, LPCs are not required to have any clinical training. See 32 M.R.S. § 13858(1).
[¶ 20] Looking at this statutory scheme as a whole, it is apparent that the Legislature intended to limit the authority to diagnose and treat mental health disorders to those licensees with clinical status. Furthermore, it is only the licensees with clinical training that are granted clinical status. If the Legislature had intended that all licensees have the authority to diagnose and treat mental health disorders, it would not have enacted, in 1999, the language of section 13858 which states that “[c]linical status grants the ability to diagnose and treat mental health disorders.” If the Legislature had intended that all licensees have diagnostic and treatment authority, this language would be mere surplusage, intended to have no effect. However, because no language is to be treated as surplusage if it can be reasonably construed, we must give meaning to this language. The reasonable construction of this language, within the context of the statutory scheme, is that only those licensees who hold clinical status have the authority under their license to diagnose and treat mental health disorders. Under the statutes, LPCs do not have clinical status. Instead, they have the authority to “assist” clients “in achieving more effective personal, emotional, social, educational and vocational development and adjustment.” 32 M.R.S. § 13851(9).
[¶ 21] Section 13858 does not give authority to all licensees to diagnose and treat mental health disorders. It is unambiguous in limiting such authority to licensees with clinical status. Because the statute is unambiguous and the legislative intention is clear, we do not defer to the Board’s interpretation.3 The Board, however, reached the correct interpretation, *278and, therefore, its interpretation must be affirmed.
C. Rulemaking
[¶ 22] Cobb argues that the Board violated the rulemaking provisions of the APA when it interpreted section 13858 in an adjudicative proceeding for the first time. Cobb makes this contention both with regard to the Board’s interpretation that LPCs are not authorized to diagnose and treat mental health disorders and with regard to its interpretation of the term “mental health disorders.” Cobb contends that the Board was first required to promulgate a rule articulating its interpretation and to do so in accordance with the rulemaking provisions of the APA, 5 M.R.S. § 8052, before it could apply the interpretation to her.
[¶ 23] The term “rule” is defined in the APA as a “regulation, standard, code, statement of policy, or other agency statement of general applicability ... that is or is intended to be judicially enforceable and implements, interprets or makes specific the law administered by the agency.” 5 M.R.S. § 8002(9)(A) (2005). However, specifically excepted from this definition are “[d]ecisions issued in adjudicatory proceedings.” 5 M.R.S. § 8002(9)(B)(3). The Board has adjudicative responsibilities, 32 M.R.S. § 13853(12) (2005), and there is no question that the interpretation of section 13858 was the result of an adjudicative proceeding. Thus, the interpretation of section 13858 does not meet the definition of “rule” in the APA, and the Board was not required to engage in formal rulemak-ing.
[¶24] As part of its adjudicative responsibility, the Board had the obligation to apply the statute that was at issue in the proceeding. When a party to an agency adjudicative proceeding raises a question about a statute’s meaning or scope and the statute is one administered by the agency, the agency must interpret it if the interpretation is necessary to the adjudicative decision. Agencies are not required to promulgate rules defining every statutory term that might be called into question. They are expected to apply statutes within their expertise as cases arise. See Mitchell v. Me. Harness Racing Comm’n, 662 A.2d 924, 926-27 (Me. 1995).
D. Due Process
[¶ 25] Cobb argues that section 13858 is void for vagueness and thereby violates the Due Process Clauses of the United States and Maine Constitutions. Essentially Cobb argues that she was unable to discern from the statute that she was not allowed to diagnose and treat.
[¶ 26] A statute is considered unconstitutionally vague when “it ‘fails to give a person of ordinary intelligence fair notice that his contemplated conduct is forbidden by the statute.’ ” Papachristou v. City of Jacksonville, 405 U.S. 156, 162, 92 S.Ct. 839, 31 L.Ed.2d 110 (1972) (quoting United States v. Harriss, 347 U.S. 612, 617, 74 S.Ct. 808, 98 L.Ed. 989 (1954)). The United States Supreme Court has stated that “economic regulation is subject to a less strict vagueness test because its subject matter is often more narrow, and because businesses, which face economic demands to plan behavior carefully, can be expected to consult relevant legislation in advance of action.” Vill. of Hoffman Estates v. The Flipside, Hoffman Estates, Inc., 455 U.S. 489, 498, 102 S.Ct. 1186, 71 L.Ed.2d 362 (1982); see Northeast Occupational Exch., Inc. v. State, 540 A.2d 1115, 1117 (Me.1988) (stating that economic regulations are sufficiently definite “if the affected person can understand what the regulations require, even though some *279doubt may arise when marginal cases are considered”).
[¶ 27] Cobb argues that because there was discussion by members of the Board during the deliberations in her case about confusion in the “counseling world” as to whether LPCs could diagnose and treat, this is an indication that the statute did not apprise licensees of the scope of their authority. However, the discussion also noted that there was a difference of opinion among counselors on this issue and that Cobb should have been aware of that controversy.
[¶ 28] The statutory scheme regulating LPCs is not void for vagueness. It specifically states that only counselors holding clinical status are authorized to diagnose and treat, and LPCs do not have clinical status. Cobb’s constitutional challenge does not succeed.
The entry is:
Judgment affirmed.
. The statute defines the categories as follows: 2. Clinical professional counselor. "Clinical professional counselor” means a professional counselor who renders or offers to render for a fee, monetary or otherwise, to individuals, families, groups, organizations or the general public, a counseling service involving the application of the principles and procedures of counseling to assess and treat intrapersonal and interpersonal problems and other dysfunctional behaviors and to assist in the overall development and adjustment of those served.
6. Marital and family therapy services. "Marital and family therapy services” means the assessment and treatment of in-trapersonal and interpersonal problems through the application of principles, methods and therapeutic techniques for the purpose of resolving emotional conflicts, modifying perceptions and behavior, enhancing communication and understanding among all family members, and preventing family and individual crises.
7. Marriage and family therapist. "Marriage and family therapist” means a person who renders or offers to render for a fee, monetary or otherwise, marital and family therapy services.
7-A. Pastoral counselor. "Pastoral counselor” means an individual who is trained and certified to provide for a fee, monetary or otherwise, pastoral counseling, which is ministry to individuals, families, couples, groups, organizations and the general public involving the application of principles and procedures of counseling to assess and treat intrapersonal and interpersonal problems and other dysfunctional behavior of a social and spiritual nature, and to assist in the overall development and healing process of those served.
9. Professional counselor. "Professional counselor” means a person who, for a fee, monetary or otherwise, renders or offers to render to individuals, families, groups, organizations or the general public a service involving the application of principles and procedures of counseling to assist those served in achieving more effective personal, emotional, social, educational and vocational development and adjustment.
32 M.R.S. § 13851(2), (6) to (7-A), (9) (2005).
. She also claims that she is entitled to an award of attorney fees if she prevails.
. Because we conclude that the statute is unambiguous and that it does not give LPCs the authority to diagnose and treat mental health disorders, we need not reach Cobb’s argument that the Board’s interpretation of the statute is arbitrary or unreasonable.