Origin: 1250–1300; ME
paire < OF < L
pāria, pl. (taken as fem. sing.) of
pār a pair.
See par 1 
Related forms: pairwise, adverb
Synonyms:
1. Pair, brace, couple, span, yoke are terms for groups of two. Pair is used of two things naturally or habitually associated in use, or necessary to each other to make a complete set: a pair of dice. It is used also of one thing composed of two similar and complementary parts: a pair of trousers. Brace is a hunter's term, used of a pair of dogs, ducks, etc., or a pair of pistols or slugs: a brace of partridges. In couple the idea of combination or interdependence has become greatly weakened; it may be used loosely for two of anything (a couple of apples), and even for more than two: I have to see a couple of people. Span is used of a matched pair of horses harnessed together side by side. Yoke applies to the two animals hitched together under a yoke for drawing and pulling: a yoke of oxen.
Usage note:When used without a modifier,
pairs is the only possible plural:
Pairs of skaters glided over the ice. When modified by a number,
pairs is the more common form, especially referring to persons:
Six pairs of masked dancers led the procession. The unmarked plural
pair is used mainly in reference to inanimate objects or nonhumans:
He has three pair (or
pairs)
of loafers. Two pair (or
pairs)
of barn owls have nested on our property.Pair signifying two individuals can take either a singular or plural verb, but it is usually followed by a plural verb and referred to by a plural pronoun:
The guilty pair have not been seen since their escape. In the sense “a set or combination of more than two objects forming a collective whole,”
pair occurs chiefly in fixed phrases:
a pair of beads; a pair of stairs. This use is now somewhat old-fashioned.
See also collective noun, couple.