Noun

(en noun)

(informal) An assistant to another person, especially to one's superior or more important person.

*{{quote-news

, year=2012 , date=May 24 , author=Nathan Rabin , title=Film: Reviews: Men In Black 3 , work=The Onion AV Club citation , page= , passage=In the abstract, Stuhlbarg’s twinkly-eyed sidekick suggests Joe Pesci in Lethal Weapon 2 by way of late-period Robin Williams with an alien twist, but Stuhlbarg makes a character that easily could have come across as precious into a surprisingly palatable, even charming man.}}

Noun

(en noun)

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

His dog has been his trusted companion for the last five years.

* Shakespeare

Here are your sons again; and I must lose / Two of the sweetest companions in the world.

(dated) A person employed to accompany or travel with another.

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

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

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

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

(astronomy) A celestial object that is associated with another.

A knight of the lowest rank in certain orders.

a companion of the Bath

(obsolete, derogatory) A fellow; a rogue.

* 1599 , , III. i. 111:

and let us knog our / prains together to be revenge on this same scald, scurvy, / cogging companion ,