conjoin vs pair

conjoin is not a noun while pair is a noun.

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

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

conjoin (noun)	pair (noun)
	two people considered as a unit
	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

conjoin (verb)	pair (verb)
make contact or come together	engage in sexual intercourse
take in marriage; married	bring two objects, ideas, or people together
	arrange in pairs
	occur in pairs
	form a pair or pairs