Pair n.
 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.
 Note: [Now mostly or quite disused.]
    Two crowns in my pocket, two pair of cards.   --Beau. & Fl.
 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.
 3. Two of a sort; a span; a yoke; a couple; a brace; as, a pair of horses; a pair of oxen.
 4. A married couple; a man and wife. “A happy pair.” --Dryden.  “The hapless pair.” --Milton.
 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.
 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]
 Note: 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.
 7. Kinematics In a mechanism, two elements, or bodies, which are so applied to each other as to mutually constrain relative motion.
 Note: ☞ 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.
 Usage: 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.”


 Pa·ri·al n. See Pair royal, under Pair, n.

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