duad vs couple

duad and couple both are nouns.

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

As nouns, duad and couple are synonyms defined as:

Other synonyms of duad include brace, couplet, distich, duet, duo, dyad, pair, span, twain, twosome, yoke.

duad (noun)	couple (noun)
two items of the same kind	a pair who associate with one another
	a pair of people who live together
	(physics) something joined by two equal and opposite forces that act along parallel lines
	two items of the same kind
	a small indefinite number

duad (verb)	couple (verb)
	engage in sexual intercourse
	link together
	bring two objects, ideas, or people together
	form a pair or pairs