Dictionary

Two similar or identical things taken together; often followed by of.

Example: I couldn't decide which of the pair of designer shirts I preferred, so I bought the pair.

Two people in a relationship, partnership or friendship.

Example: Spouses should make a great pair.

Used with binary nouns (often in the plural to indicate multiple instances, since such nouns are plural only, except in some technical contexts)

Example: a pair of scissors; two pairs of spectacles; several pairs of jeans

A couple of working animals attached to work together, as by a yoke.

Example: A pair is harder to drive than two mounts with separate riders.

To group into one or more sets of two.

Example: The wedding guests were paired boy/girl and groom's party/bride's party.

To bring two (animals, notably dogs) together for mating.

To engage (oneself) with another of opposite opinions not to vote on a particular question or class of questions.

To suit; to fit, as a counterpart.

To impair, to make worse.

To become worse, to deteriorate.