dual vs three-fold

dual and three-fold both are adjectives.

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

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

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

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

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