pair 
(pâr)
(pâr)n. pl. pair or pairs
1. Two corresponding persons or items, similar in form or function and matched or associated: a pair of shoes.
2. One object composed of two joined, similar parts that are dependent upon each other: a pair of pliers.
3.
a. Two persons who are married, engaged, or dating.
b. Two persons who have something in common and are considered together: a pair of hunters.
c. Two mated animals.
d. Two animals joined together in work.
4. Games Two playing cards of the same denomination.
5. Two members of a deliberative body with opposing opinions on a given issue who agree to abstain from voting on the issue, thereby offsetting each other.
6. Chemistry An electron pair.
v. paired, pair·ing, pairs
v.tr.
1. To arrange in sets of two; couple: The golfers are paired in twosomes for this round of play.
2. To combine or join (one person or thing) with another to form a pair: a director pairing his favorite actor with an unknown; a salad that is paired with a fine dressing.
v.intr.
1. To form pairs or a pair: The people on the dance floor paired up.
2. To join with another in love or mating.
[Middle English, from Old French paire, from Latin paria, equals, pl. of pār, a pair, from pār, equal; see perə-2 in the Appendix of Indo-European roots.]
Usage Note: The noun pair can be followed by a singular or plural verb. The singular is always used when pair denotes the set taken as a single entity: This pair of shoes is on sale. A plural verb is used when the members are considered as individuals: The pair are working more harmoniously now. After a number other than one, pair itself can be either singular or plural, but the plural is now more common: I bought six pairs (or pair) of shoes.