GI, GIs – This term describes military personnel. Its origins include its use as an abbreviation for government issue and similar terms. Soldier is the preferred term when describing a service member in the Army, Marine is preferred for those in the U.S. Marines, sailor is preferred for those serving in the Navy and airman is preferred for service members (regardless of gender) in the Air Force. Note that unless the term is at the start of a sentence, lowercase soldier, sailor and airman but capitalize Marine.
government – Always lowercase and spell out: federal government, state government, U.S. government.