4. dual of or belonging to a grammatical category of number, as in Old English, Old Russian, or Arabic, used to indicate that a word denotes two persons or things.
Etymology: (1535–45; < L duālis containing two, relating to a pair)
Definition of 'dual'
Princeton's WordNet
1. (adj)double, dual, duple consisting of or involving two parts or components usually in pairs "an egg with a double yolk"; "a double (binary) star"; "double doors"; "dual controls for pilot and copilot"; "duple (or double) time consists of two (or a multiple of two) beats to a measure"
2. (adj)double, dual, twofold, two-fold, treble, threefold, three-fold having more than one decidedly dissimilar aspects or qualities "a double (or dual) role for an actor"; "the office of a clergyman is twofold; public preaching and private influence"- R.W.Emerson; "every episode has its double and treble meaning"-Frederick Harrison
3. (adj)dual a grammatical numbercategory referring to two items or units as opposed to one item (singular) or more than two items (plural) "ancient Greek had the dual form but it has merged with the plural form in modern Greek"
Definition of 'dual'
Webster Dictionary
1. (adj)dual expressing, or consisting of, the number two; belonging to two; as, the dual number of nouns, etc. , in Greek