adj.1. Composed of two usually like or complementary parts; double: dual controls for pilot and copilot; a car with dual exhaust pipes.
2. Having a double character or purpose: a belief in the dual nature of reality.
3. Grammar Of, relating to, or being a number category that indicates two persons or things, as in Greek, Sanskrit, and Old English.
n. Grammar 1. The dual number.
2. An inflected form of a noun, adjective, pronoun, or verb used with two items or people.