deuce vs duad

deuce and duad both are nouns.

Word	Noun	Adjective	Verb	Adverb
deuce	Yes	No	No	No
duad	Yes	No	No	No

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

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

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

deuce (noun)	duad (noun)
one of the four playing cards in a deck that have two spots	two items of the same kind
a word used in exclamations of confusion
the cardinal number that is the sum of one and one or a numeral representing this number
a tie in tennis or table tennis that requires winning two successive points to win the game