\Pair\, n. [F. paire, LL. paria, L. paria, pl. of par pair,
fr. par, adj., equal. Cf. {Apparel}, {Par} equality, {Peer}
an equal.]
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, except as to stairs.]
            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
   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, or on issues of a party nature during a
   specified time; as, there were two pairs on the final
   vote. [Parliamentary Cant]
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.''

\Pair\, v. i. [imp. & p. p. {Paired}; p. pr. & vb. n.
{Pairing}.]
1. To be joined in paris; to couple; to mate, as for
   breeding.
2. To suit; to fit, as a counterpart.
         My heart was made to fit and pair with thine.
                                               --Rowe.
3. 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.

\Pair\, v. t.
1. 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.
2. 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}. (Zo["o]l.) See under {Fin}.

\Pair\, v. t. [See {Impair}.]
To impair. [Obs.] --Spenser.