1a person or animal with whom one spends a lot of time or with whom one travels:his travelling companion figurativefear became my constant companion
a person who shares the experiences of another, especially when these are unpleasant or unwelcome:my companions in misfortune
a person’s long-term sexual partner outside marriage:Steve and his live-in companion
a person, usually a woman, employed to live with and assist another:she brought along her companion, whose drab attire set off her employer’s brilliance
Astronomy a star, galaxy, or other celestial object that is close to or associated with another:the small, hot, and compact companion of Sirius was discovered in 1915 [as modifier]:a small companion galaxy
2each of a pair of things intended to complement or match each other: [as modifier]:a companion volume
[usually in names] a book that provides information about a particular subject:the Oxford Companion to English Literature
British dated a piece of equipment containing several objects used in a particular activity:a traveller’s companion
3 (Companion) a member of the lowest grade of certain orders of knighthood:a Companion of the Order of Canada
