For the purpose of this subchapter—

(1) “agency” means an Executive agency and a military department;

(2) “employee” means an employee in or under an agency who is a citizen or national of the United States or an alien admitted to the United States for permanent residence, but does not include a part-time or intermittent employee or native labor casually hired on an hourly or daily basis. However, such an employee who enters a status listed in paragraph (5)(A)-(E) of this section—

(A) inside the continental United States; or

(B) who is a resident at or in the vicinity of his place of employment in a territory or possession of the United States or in a foreign country and who was not living there solely as a result of his employment;

is an employee for the purpose of this subchapter only on a determination by the head of the agency concerned that this status is the proximate result of employment by the agency;

(3) “dependent” means—

(A) a wife;

(B) an unmarried child (including an unmarried dependent stepchild or adopted child) under 21 years of age;

(C) a dependent mother or father;

(D) a dependent designated in official records; and

(E) an individual determined to be dependent by the head of the agency concerned or his designee;

(4) “active service” means active Federal service by an employee;

(5) “missing status” means the status of an employee who is in active service and is officially carried or determined to be absent in a status of—

(A) missing;

(B) missing in action;

(C) interned in a foreign country;

(D) captured, beleaguered, or besieged by a hostile force; or

(E) detained in a foreign country against his will;

but does not include the status of an employee for a period during which he is officially determined to be absent from his post of duty without authority; and

(6) “pay and allowances” means—

(A) basic pay;

(B) special pay;

(C) incentive pay;

(D) basic allowance for housing;

(E) basic allowance for subsistence; and

(F) station per diem allowances for not more than 90 days.