What is Companion?

Companion definition and meaning on Dictionary terms:
a person who is frequently in the company of, associates with, or accompanies another: my son and his two companions.
a person employed to accompany, assist, or live with another in the capacity of a helpful friend.
a mate or match for something: White wine is the usual companion of fish.
a handbook or guide: a bird watcher’s companion.
a member of the lowest rank in an order of knighthood or of a grade in an order.

Also called companion star, comes. Astronomy. the fainter of the two stars that constitute a double star.Compare primary(def 19b).
Obsolete. a fellow.

verb (used with object)
to be a companion to; accompany.