41 CFR 301-1.2 - What is an
An “employee” is:
(a) An individual employed by an agency, regardless of status or rank; or
(b) An individual employed intermittently in Government service as an expert or consultant and paid on a daily when-actually-employed (WAE) basis; or
(c) An individual serving without pay or at $1 a year (also referred to as “invitational traveler”).