29 U.S.C. § 2101: Definitions; exclusions from definition of loss of employment

100 or more employees, excluding part-time employees; or 100 or more employees who in the aggregate work at least 4,000 hours per week (exclusive of hours of overtime); the term “plant closing” means the permanent or temporary shutdown of a single site of employment, or one or more facilities or operating units within a single site of employment, if the shutdown results in an employment loss at the single site of employment during any 30-day period for 50 or more employees excluding any part-time employees; is not the result of a plant closing; and at least 33 percent of the employees (excluding any part-time employees); and at least 50 employees (excluding any part-time employees); or at least 500 employees (excluding any part-time employees); the term “representative” means an exclusive representative of employees within the meaning of section 159(a) or 158(f) of this title or section 152 of title 45 ; the term “affected employees” means employees who may reasonably be expected to experience an employment loss as a consequence of a proposed plant closing or mass layoff by their employer; subject to subsection (b), the term “employment loss” means (A) an employment termination, other than a discharge for cause, voluntary departure, or retirement, (B) a layoff exceeding 6 months, or (C) a reduction in hours of work of more than 50 percent during each month of any 6-month period; the term “unit of local government” means any general purpose political subdivision of a State which has the power to levy taxes and spend funds, as well as general corporate and police powers; and the term “part-time employee” means an employee who is employed for an average of fewer than 20 hours per week or who has been employed for fewer than 6 of the 12 months preceding the date on which notice is required. In the case of a sale of part or all of an employer’s business, the seller shall be responsible for providing notice for any plant closing or mass layoff in accordance with section 2102 of this title , up to and including the effective date of the sale. After the effective date of the sale of part or all of an employer’s business, the purchaser shall be responsible for providing notice for any plant closing or mass layoff in accordance with section 2102 of this title . Notwithstanding any other provision of this chapter, any person who is an employee of the seller (other than a part-time employee) as of the effective date of the sale shall be considered an employee of the purchaser immediately after the effective date of the sale. the employer offers to transfer the employee to a different site of employment within a reasonable commuting distance with no more than a 6-month break in employment; or the employer offers to transfer the employee to any other site of employment regardless of distance with no more than a 6-month break in employment, and the employee accepts within 30 days of the offer or of the closing or layoff, whichever is later.