doubleton vs pair

doubleton and pair both are nouns.

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

As nouns, pair is a hypernym of doubleton; that is, pair is a word with a broader meaning than doubleton:

doubleton: (bridge) a pair of playing cards that are the only cards in their suit in the hand dealt to a player
pair: two items of the same kind

Other hypernyms of doubleton include brace, couple, couplet, distich, duad, duet, duo, dyad, span, twain, twosome, yoke.

doubleton (noun)	pair (noun)
(bridge) a pair of playing cards that are the only cards in their suit in the hand dealt to a player	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

doubleton (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