ETYM French compagnie, from Old Fren. compaing. Related to Companion.
1. A social gathering of guests or companions.
2. The state of being with someone; SYN. comradeship, companionship, good fellowship, fellowship, society.
3. An institution created to conduct business.
4. Organization of performers and associated personnel (especially theatrical); SYN. troupe.
5. Small military unit; usually two or three platoons.
6. A unit of firefighters including their equipment.

CIA

1. A chartered commercial organization or medieval trade guild.
2. An association of persons for carrying on a commercial or industrial enterprise
3. Those members of a partnership firm whose names do not appear in the firm name .

In the army, a subunit of a battalion. It consists of about 120 soldiers, and is commanded by a captain in the US army and by a major in the British army. Four or five companies make a battalion.

To be a companion to somebody; SYN. companion, accompany, keep company.