PAIR, n. [L. par; Heb. to join, couple or associate.]

1. Two things of a kind, similar in form, applied to the same purpose, and suited to each other or used together; as, a pair of gloves or stockings; a pair of shoes; a pair of oxen or horses.
2. Two of a sort; a couple; a brace; as, a pair of nerves; a pair of doves. – Luke ii.

1. To be joined in pairs; to couple; as, birds pair in summer.
2. To suit; to fit; as a counterpart. Ethelinda, / My heart was made to fit and pair with thine. – Rowe.

1. To unite in couples; as, minds paired in heaven. – Dryden.
2. To unite as correspondent, or rather to contrast. Glossy jet is paired with shining white. – Pope.

To impair. [See Impair.]

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, except as to stairs.]
   
   

   Two crowns in my pocket, two pair of cards. Beau. & Fl.

2. To be joined in paris] to couple; to mate, as for breeding.
3. To unite in couples; to form a pair of; to bring together, as things which belong together, or which complement, or are adapted to one another.
   
   

   Glossy jet is paired with shining white. Pope.

4. To impair.
   
   
   [Obs.] Spenser.
5. 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.
6. To suit; to fit, as a counterpart.
   
   

   My heart was made to fit and pair with thine. Rowe.

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

   Paired fins. (Zoöl.) See under Fin.

8. Two of a sort; a span; a yoke; a couple; a brace; as, a pair of horses; a pair of oxen.
9. Same as To pair off. See phrase below.
   
   

   To pair off, to separate from a company 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.

10. A married couple; a man and wife.
    
    
    "A happy pair." Dryden. "The hapless pair." Milton.
11. A single thing, composed of two pieces fitted to each other and used together; as, a pair of scissors; a pair of tongs; a pair of bellows.
12. Two members of opposite parties or opinion, as in a parliamentary body, who mutually agree not to vote on a given question, or on issues of a party nature during a specified time; as, there were two pairs on the final vote.
    
    
    [Parliamentary Cant]
13. In a mechanism, two elements, or bodies, which are so applied to each other as to mutually constrain relative motion.
    
    

    * 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.

    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.]

    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."