du·al / ˈd(y)oōəl/ • adj. 1. consisting of two parts, elements, or aspects: their dual role at work and home. ∎  Gram. (in some languages) denoting an inflection that refers to exactly two people or things (as distinct from singular and plural): Old English has dual number for first- and second-person pronouns. ∎  (in an aircraft) using dual controls: a dual flight.2. (often dual to) Math. (of a theorem, expression, etc.) related to another by the interchange of particular pairs of terms, such as “point” and “line.”• n. 1. Gram. a dual form of a word. ∎  the dual number.2. Math. a theorem, expression, etc., that is dual to another.DERIVATIVES: du·al·ize / -ˌlīz/ v.du·al·ly adv.

dual XVII. — L. duālis, f. duo TWO; see -AL 1.
Hence dualism XVIII. So duality XIV. — late L.

dual See duality.