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}.]
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.''