5 U.S.C. § 5521
Definitions
For the purpose of this subchapter—
(1)
“agency” means—
(A)
an Executive agency;
(B)
the judicial branch;
(C)
the Library of Congress;
(D)
the Government Publishing Office; and
(E)
the government of the District of Columbia;
(2)
“employee” means an individual employed in or under an agency;
(3)
“head of each agency” means—
(A)
the Director of the Administrative Office of the United States Courts with respect to the judicial branch; and
(B)
the Mayor of the District of Columbia with respect to the government of the District of Columbia; and
(4)
“United States”, when used in a geographical sense, means the several States and the District of Columbia.
( Pub. L. 89–554 , Sept. 6, 1966 , 80 Stat. 479 ; Pub. L. 90–623, § 1(10) , Oct. 22, 1968 , 82 Stat. 1312 ; Pub. L. 96–54, § 2(a)(31) , Aug. 14, 1979 , 93 Stat. 383 ; Pub. L. 113–235, div. H, title I, § 1301(b) , Dec. 16, 2014 , 128 Stat. 2537 .)