Merriam-Webster Collegiate Dictionary - pair

 I. noun  (plural ~s or ~)  Etymology: Middle English ~e, from Anglo-French, from Latin paria equal things, from neuter plural of par equal  Date: 14th century  1.  a.  (1) two corresponding things designed for use together a ~ of shoes  (2) two corresponding bodily parts or members a ~ of hands  b. something made up of two corresponding pieces a ~ of trousers  2.  a. two similar or associated things: as  (1) two mated animals  (2) a couple in love, engaged, or married were a devoted ~  (3) two playing cards of the same value or denomination and especially of the same rank  (4) two horses harnessed side by side  (5) two members of a deliberative body that agree not to vote on a specific issue during a time agreed on; also an agreement not to vote made by the two members  b. a partnership especially of two players in a contest against another partnership  3. chiefly dialect a set or series of small objects (as beads)  II. verb  Date: 1606  transitive verb  1.  a. to make a ~ of — often used with off or up ~ed off the animals  b. to cause to be a member of a ~  c. to arrange a voting ~ between  2. to arrange in ~s  intransitive verb  1. to constitute a member of a ~ a sock that didn't ~  2.  a. to become associated with another — often used with off or up ~ed up with an old friend  b. to become grouped or separated into ~s — often used with off ~ed off for the next dance