pair

Two corresponding persons or items, similar in form or function and matched or associated.

One object composed of two joined, similar parts that are dependent upon each other.

Two persons who are married, engaged, or dating.

Two persons who have something in common and are considered together.

Two mated animals.

Two animals joined together in work.

Two playing cards of the same denomination.

Two members of a deliberative body with opposing opinions on a given issue who agree to abstain from voting on the issue, thereby offsetting each other.

An electron pair.