three-fold vs dual

three-fold and dual both are adjectives.

Word	Noun	Adjective	Verb	Adverb
three-fold	No	Yes	No	No
dual	No	Yes	No	No

As adjectives, three-fold and dual are synonyms defined as:

three-fold and dual: having more than one decidedly dissimilar aspects or qualities

Other synonyms of three-fold include double, threefold, treble, two-fold, twofold.

three-fold (adjective)	dual (adjective)
three times as great or many	consisting of or involving two parts or components usually in pairs
having more than one decidedly dissimilar aspects or qualities	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