duple vs dual

duple and dual both are adjectives.

Word	Noun	Adjective	Verb	Adverb
duple	No	Yes	No	No
dual	No	Yes	No	No

As adjectives, duple and dual are synonyms defined as:

duple and dual: consisting of or involving two parts or components usually in pairs

Other synonyms of duple include double.

duple (adjective)	dual (adjective)
consisting of or involving two parts or components usually in pairs	consisting of or involving two parts or components usually in pairs
	a grammatical number category referring to two items or units as opposed to one item (singular) or more than two items (plural)
	having more than one decidedly dissimilar aspects or qualities