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 Printing 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.
