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dual 音标拼音: [d'uəl] [d'ul] a. 双重的,双的
n. 双数 双重的,双的双数 dual 逻辑被动自动对偶 LPSD dual 自对偶 dual 双 dual adj 1: 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" [synonym: {double}, {dual}, {duple}] 2: 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 [synonym: {double}, {dual}, {twofold}, {two-fold}, {treble}, {threefold}, {three- fold}] 3: a grammatical number category 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" Dual \Du"al\, a. [L. dualis, fr. duo two. See {Two}.] Expressing, or consisting of, the number two; belonging to two; as, the dual number of nouns, etc., in Greek. [1913 Webster] Here you have one half of our dual truth. --Tyndall. [1913 Webster] 43 Moby Thesaurus words for "dual": Janus-like, ambidextrous, bifacial, bifold, biform, bifurcated, bilateral, binary, binate, biparous, bipartisan, bipartite, bivalent, conduplicate, dichotomous, disomatous, double, double-barreled, double-faced, duadic, dualistic, duple, duplex, duplicate, duplicated, dyadic, geminate, geminated, identical, matched, paired, second, secondary, twain, twin, twinned, two, two-faced, two-level, two-ply, two-sided, two-story, twofold meaning of dual. Loosely, where there is some binary symmetry of a theory, the image of what you look at normally under this symmetry is referred to as the dual of your normal things. In linear algebra for example, for any {vector space} V, over a {field}, F, the vector space of {linear maps} from V to F is known as the dual of V. It can be shown that if V is finite-dimensional, V and its dual are {isomorphic} (though no isomorphism between them is any more natural than any other). There is a natural {embedding} of any vector space in the dual of its dual: V -> V'': v -> (V': w -> wv : F) (x' is normally written as x with a horizontal bar above it). I.e. v'' is the linear map, from V' to F, which maps any w to the scalar obtained by applying w to v. In short, this double-dual mapping simply exchanges the roles of function and argument. It is conventional, when talking about vectors in V, to refer to the members of V' as covectors. (1997-03-16)
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