The term “person” means one or more individuals, partnerships, associations, labor organizations, corporations, business trusts, legal representatives, or any organized groups of persons.

The term “employer” means a person engaged in an industry affecting commerce who has twenty or more employees for each working day in each of twenty or more calendar weeks in the current or preceding calendar year: Provided, That prior to June 30, 1968, employers having fewer than fifty employees shall not be considered employers. The term also means (1) any agent of such a person, and (2) a State or political subdivision of a State and any agency or instrumentality of a State or a political subdivision of a State, and any interstate agency, but such term does not include the United States, or a corporation wholly owned by the Government of the United States.

The term “employment agency” means any person regularly undertaking with or without compensation to procure employees for an employer and includes an agent of such a person; but shall not include an agency of the United States.

The term “labor organization” means a labor organization engaged in an industry affecting commerce, and any agent of such an organization, and includes any organization of any kind, any agency, or employee representation committee, group, association, or plan so engaged in which employees participate and which exists for the purpose, in whole or in part, of dealing with employers concerning grievances, labor disputes, wages, rates of pay, hours, or other terms or conditions of employment, and any conference, general committee, joint or system board, or joint council so engaged which is subordinate to a national or international labor organization.

The term “employee” means an individual employed by any employer except that the term “employee” shall not include any person elected to public office in any State or political subdivision of any State by the qualified voters thereof, or any person chosen by such officer to be on such officer’s personal staff, or an appointee on the policymaking level or an immediate adviser with respect to the exercise of the constitutional or legal powers of the office. The exemption set forth in the preceding sentence shall not include employees subject to the civil service laws of a State government, governmental agency, or political subdivision. The term “employee” includes any individual who is a citizen of the United States employed by an employer in a workplace in a foreign country.

The term “commerce” means trade, traffic, commerce, transportation, transmission, or communication among the several States; or between a State and any place outside thereof; or within the District of Columbia, or a possession of the United States; or between points in the same State but through a point outside thereof.

The term “industry affecting commerce” means any activity, business, or industry in commerce or in which a labor dispute would hinder or obstruct commerce or the free flow of commerce and includes any activity or industry “affecting commerce” within the meaning of the Labor-Management Reporting and Disclosure Act of 1959 [29 U.S.C. 401 et seq.].

The term “State” includes a State of the United States, the District of Columbia, Puerto Rico, the Virgin Islands, American Samoa, Guam, Wake Island, the Canal Zone, and Outer Continental Shelf lands defined in the Outer Continental Shelf Lands Act [43 U.S.C. 1331 et seq.].

The term “firefighter” means an employee, the duties of whose position are primarily to perform work directly connected with the control and extinguishment of fires or the maintenance and use of firefighting apparatus and equipment, including an employee engaged in this activity who is transferred to a supervisory or administrative position.

The term “law enforcement officer” means an employee, the duties of whose position are primarily the investigation, apprehension, or detention of individuals suspected or convicted of offenses against the criminal laws of a State, including an employee engaged in this activity who is transferred to a supervisory or administrative position. For the purpose of this subsection, “detention” includes the duties of employees assigned to guard individuals incarcerated in any penal institution.

The term “compensation, terms, conditions, or privileges of employment” encompasses all employee benefits, including such benefits provided pursuant to a bona fide employee benefit plan.