two vs pair

two and pair both are nouns.

Word	Noun	Adjective	Verb	Adverb
two	Yes	Yes	No	No
pair	Yes	No	Yes	No

As nouns, pair is a hyponym of two; that is, pair is a word with a more specific, narrower meaning than two:

two: the cardinal number that is the sum of one and one or a numeral representing this number
pair: two items of the same kind

Other hyponyms of two include craps, snake eyes, brace, couple, couplet, distich, duad, duet, duo, dyad, span, twain, twosome, yoke.

two (noun)	pair (noun)
one of the four playing cards in a deck that have two spots	two people considered as a unit
the cardinal number that is the sum of one and one or a numeral representing this number	a set of two similar things considered as a unit
	a poker hand with 2 cards of the same value
	two items of the same kind

two (adjective)	pair (adjective)
being one more than one

two (verb)	pair (verb)
	engage in sexual intercourse
	bring two objects, ideas, or people together
	arrange in pairs
	occur in pairs
	form a pair or pairs