companion, comrade, fellow, familiar, associate (noun)

a friend who is frequently in the company of another

"drinking companions"; "comrades in arms"

companion, fellow traveler, fellow traveller (noun)

a traveler who accompanies you

companion (verb)

one paid to accompany or assist or live with another

company, companion, accompany, keep company (verb)

be a companion to somebody

companion (Noun)

A friend, acquaintance, or partner; someone with whom one spends time or keeps company

companion (Noun)

A person employed to accompany or travel with another.

companion (Noun)

The framework on the quarterdeck of a sailing ship through which daylight entered the cabins below.

companion (Noun)

The covering of a hatchway on an upper deck which leads to the companionway; the stairs themselves.

companion (Noun)

A knot in whose neighborhood another, specified, knot meets every meridian disk.

companion (Noun)

A thing or phenomenon that is closely associated with another thing, phenomenon, or person.

companion (Noun)

A celestial object that is associated with another.

companion (Verb)

To qualify as a companion; to make equal.

Companion

In the long-running BBC television science fiction programme Doctor Who and related works, the term "companion" refers to a character who travels with, or shares the adventures of the Doctor. In most Doctor Who stories, the primary companion acts as an audience surrogate. He or she provides the lens through which the viewer is introduced to the series. The companion character, many times, furthers the story by asking questions and getting into trouble, or by helping, rescuing or challenging the Doctor. This designation is applied to a character by the show's producers, and appears in the BBC's promotional material and off-screen fictional terminology. Until the modern revival of the series in 2005, the term was rarely used on-screen. The Doctor also refers to the show's other leads as his "friends" or "assistants"; the British press have also used the latter term.