U.S. Labor Law Glossary: Key Terms, Definitions, and Legal Concepts

The U.S. labor law system spans more than 180 federal statutes and regulations, each carrying its own vocabulary of defined terms that carry precise legal weight. This glossary page covers the foundational concepts, phrases, and classifications used across federal labor and employment law — from collective bargaining to wage standards to discrimination protections. Understanding these terms is essential for interpreting statutory text, agency guidance, and court decisions accurately. For broader statutory context, the U.S. Labor Law Overview provides the structural framework within which these definitions operate.

Definition and scope

Labor law terminology operates differently from general legal vocabulary. Terms such as "employee," "employer," "supervisor," and "wages" carry statutory definitions that may diverge significantly from their ordinary-language meanings — and those definitions can vary across statutes. The National Labor Relations Act (NLRA), codified at 29 U.S.C. §§ 151–169, defines "employee" to exclude supervisors, independent contractors, and agricultural workers. The Fair Labor Standards Act (FLSA), codified at 29 U.S.C. §§ 201–219, uses a broader definition of "employee" tied to the economic-realities test rather than the common-law control test.

Scope distinctions also apply geographically and by sector. Private-sector workers in interstate commerce fall primarily under NLRA jurisdiction; federal government employees are covered by the Civil Service Reform Act of 1978 and the Federal Labor Relations Authority; railway and airline employees are governed by the Railway Labor Act. Approximately 14 million U.S. workers belong to unions (Bureau of Labor Statistics, Union Members Summary, 2023), making the precise definition of collective rights terminology consequential for a large segment of the workforce.

How it works

Labor law terms function as operative triggers within statutory and regulatory frameworks. Whether a worker qualifies as an "employee" under a given statute determines whether the entire protective regime of that statute applies. The following glossary entries reflect definitions drawn from named federal sources:

1. At-will employment — A default common-law doctrine, recognized in 49 states, under which either party may terminate the employment relationship at any time for any lawful reason or no reason. Statutory exceptions include Title VII, the ADEA, and the NLRA's anti-retaliation provisions. See At-Will Employment Doctrine for jurisdictional nuances.

2. Collective bargaining — The process by which an employer and a union representing employees negotiate in good faith over wages, hours, and terms and conditions of employment, as required under NLRA Section 8(d) (29 U.S.C. § 158(d)).

3. Unfair labor practice (ULP) — An act by an employer or labor organization that violates specific provisions of the NLRA, adjudicated by the National Labor Relations Board. Employer ULPs include interfering with organizing rights; union ULPs include coercing members in the exercise of their Section 7 rights.

4. Protected concerted activity — Action taken by 2 or more employees (or a single employee acting on behalf of others) for mutual aid or protection, protected under NLRA Section 7 (29 U.S.C. § 157).

5. Exempt vs. non-exempt employee (FLSA) — Employees classified as exempt from FLSA overtime requirements must satisfy both a salary-level test (currently $684 per week as of the 2019 rule (DOL Wage and Hour Division)) and a duties test. Non-exempt employees must receive 1.5× their regular rate for hours worked beyond 40 in a workweek.

6. Prevailing wage — The wage rate determined by the Department of Labor under the Davis-Bacon Act (40 U.S.C. §§ 3141–3148) for laborers on federally funded construction contracts, set at the rate paid to the majority of workers in a given locality and trade.

7. Joint employer — A legal finding that two or more entities share or co-determine the essential terms and conditions of employment, making both potentially liable under the NLRA or FLSA. The standard has been revised multiple times by NLRB rulemaking; see Joint Employer Doctrine.

8. Mandatory arbitration — A contractual provision requiring employees to resolve workplace disputes through private arbitration rather than litigation, the enforceability of which under the Federal Arbitration Act (9 U.S.C. §§ 1–16) has been addressed repeatedly by the U.S. Supreme Court. See Mandatory Arbitration in Employment.

9. Retaliation — An adverse employment action taken against a worker because the worker engaged in a protected activity (such as filing a complaint, participating in an investigation, or organizing). Retaliation prohibitions appear in more than 20 federal statutes, including the FLSA, NLRA, FMLA, and Title VII.

10. WARN Act notice — A requirement under the Worker Adjustment and Retraining Notification Act (29 U.S.C. §§ 2101–2109) that employers with 100 or more full-time employees provide 60 calendar days' advance written notice before a plant closing or mass layoff affecting 50 or more workers at a single site. See Worker Adjustment and Retraining Notification Act.

Common scenarios

Labor law terminology arises in predictable dispute contexts. The following represent the four most frequently litigated classification and definitional disputes before federal agencies and courts:

Independent contractor vs. employee misclassification — A business that labels workers as independent contractors but exercises sufficient behavioral and financial control may face FLSA back-pay liability, FICA tax assessments, and NLRA coverage questions. The Department of Labor issued a final rule in 2024 (DOL RIN 1235-AA43) restoring a multi-factor economic-realities test. See Independent Contractor vs. Employee Classification for the full test structure.

Supervisor exclusion disputes — Under NLRA Section 2(11) (29 U.S.C. § 152(11)), an employee with authority to hire, fire, discipline, or responsibly direct other employees using independent judgment is classified as a supervisor and excluded from bargaining unit protections. Charge nurses, lead technicians, and team leads frequently fall into this contested zone.

FLSA exemption challenges — The FLSA's white-collar exemptions (executive, administrative, professional) require employers to demonstrate both salary threshold compliance and a qualifying duties test. Courts have held that job titles alone do not determine exempt status; actual day-to-day duties govern the analysis per 29 C.F.R. Part 541 (Electronic Code of Federal Regulations).

Covered employer thresholds — Major statutes impose employer-size thresholds: Title VII and the ADA apply to employers with 15 or more employees (42 U.S.C. § 2000e(b)); the ADEA applies to employers with 20 or more employees (29 U.S.C. § 630(b)); the FMLA applies to employers with 50 or more employees within 75 miles of the worksite.

Decision boundaries

The distinction between terms that appear synonymous often determines liability. Three contrasts are particularly significant:

Discharge vs. constructive discharge — A direct termination is a unilateral employer act ending employment. Constructive discharge occurs when working conditions become so intolerable that a reasonable person would feel compelled to resign; courts treat it as equivalent to a termination for discrimination and retaliation purposes. The U.S. Supreme Court addressed the standard in Pennsylvania State Police v. Suders, 542 U.S. 129 (2004).

Strike vs. lockout — A strike is a work stoppage initiated by employees. A lockout is initiated by the employer. Both are lawful economic weapons under the NLRA in most circumstances, but the legal protections available to workers differ: employees engaged in an economic strike may be permanently replaced, while unfair-labor-practice strikers may not be. See Strikes and Labor Actions Law for the full classification framework.

Disparate treatment vs. disparate impact — Disparate treatment is intentional discrimination against an individual based on a protected characteristic. Disparate impact refers to a facially neutral policy that disproportionately affects a protected class without business justification, as established under Griggs v. Duke Power Co., 401 U.S. 424 (1971), and codified in the Civil Rights Act of 1991 ([42 U.S.C. § 2000e-2(k)](https://uscode.house.