duality vs dual

duality is a noun but dual is not a noun.

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

duality (noun)	dual (noun)
(physics) the property of matter and electromagnetic radiation that is characterized by the fact that some properties can be explained best by wave theory and others by particle theory
(geometry) the interchangeability of the roles of points and planes in the theorems of projective geometry
being twofold; a classification into two opposed parts or subclasses

duality (adjective)	dual (adjective)
	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