1. A number of things resembling one another, or belonging together; a set; as, a pair or flight of stairs. “A pair of beads.” Chaucer. Beau. & Fl. “Four pair of stairs.” Macaulay. [ Now mostly or quite disused. ] [ 1913 Webster ]

Two crowns in my pocket, two pair of cards. Beau. & Fl. [ 1913 Webster ]

2. Two things of a kind, similar in form, suited to each other, and intended to be used together; as, a pair of gloves or stockings; a pair of shoes. [ 1913 Webster ]

3. Two of a sort; a span; a yoke; a couple; a brace; as, a pair of horses; a pair of oxen. [ 1913 Webster ]

4. A married couple; a man and wife. “A happy pair.” Dryden. “The hapless pair.” Milton. [ 1913 Webster ]

5. A single thing, composed of two pieces fitted to each other and used together; as, a pair of scissors; a pair of pants; a pair of tongs; a pair of bellows. [ 1913 Webster ]

6. Two members of opposite parties or opinion, as in a parliamentary body, who mutually agree not to vote on a given question (in order, for example, to allow the members to be absent during the vote without affecting the outcome of the vote), or on issues of a party nature during a specified time; as, there were two pairs on the final vote. [ Parliamentary Cant ] A member who is thus paired with one who would have voted oppositely is said to be paired for or paired against a measure, depending on the member's position. [ 1913 Webster +PJC ]

7. (Kinematics) In a mechanism, two elements, or bodies, which are so applied to each other as to mutually constrain relative motion. [ 1913 Webster ]

☞ Pairs are named in accordance with the kind of motion they permit; thus, a journal and its bearing form a turning pair, a cylinder and its piston a sliding pair, a screw and its nut a twisting pair, etc. Any pair in which the constraining contact is along lines or at points only (as a cam and roller acting together), is designated a higher pair; any pair having constraining surfaces which fit each other (as a cylindrical pin and eye, a screw and its nut, etc.), is called a lower pair. [ 1913 Webster ]

Pair royal (pl. Pairs Royal) three things of a sort; -- used especially of playing cards in some games, as cribbage; as three kings, three “eight spots” etc. Four of a kind are called a double pair royal. “Something in his face gave me as much pleasure as a pair royal of naturals in my own hand.” Goldsmith. “That great pair royal of adamantine sisters [ the Fates ].” Quarles. [ Written corruptly parial and prial. ] [ 1913 Webster ]

Syn. -- Pair, Flight, Set. Originally, pair was not confined to two things, but was applied to any number of equal things (pares), that go together. Ben Jonson speaks of a pair (set) of chessmen; also, he and Lord Bacon speak of a pair (pack) of cards. A “pair of stairs” is still in popular use, as well as the later expression, “flight of stairs.” [ 1913 Webster ]

2. To suit; to fit, as a counterpart. [ 1913 Webster ]

My heart was made to fit and pair with thine. Rowe. [ 1913 Webster ]

3. Same as To pair off. See phrase below. [ 1913 Webster ]

To pair off, to separate from a group in pairs or couples; specif. (Parliamentary Cant), to agree with one of the opposite party or opinion to abstain from voting on specified questions or issues. See Pair, n., 6. [ 1913 Webster ]

Glossy jet is paired with shining white. Pope. [ 1913 Webster ]

2. To engage (one's self) with another of opposite opinions not to vote on a particular question or class of questions. [ Parliamentary Cant ] [ 1913 Webster ]

Paired fins. (Zool.) See under Fin. [ 1913 Webster ]

2. (Botany) Growing in pairs on either side of a stem; -- of leaves etc. alternate
Syn. -- opposite. [ WordNet 1.5 ]

3. Mated sexually. [ WordNet 1.5 ]

2. See To pair off, under Pair, v. i. [ 1913 Webster ]

Pairing time, the time when birds or other animals pair. [ 1913 Webster ]