Etymology: Variant of be- prefix.

Etymology: < Latin bi- (earlier dui-, cognate with Greek δι-, Sanskrit dvi-) ‘twice, doubly, having two, two-,’ which is in Latin a prefix of adjectives, occasionally of nouns, rarely of verbs (e.g. bipertīre). The earliest Latin adjectives of this type are formed by simply prefixing bi- either to adjective (and verb-) stems, as bifer, bifidus, bijugus, bisonus, or to noun- (and adjective) stems, as bicolor, biceps, bifrons, bifurcus, bigener; later in all probability, and more evidently mere compounds, are those in which bi- is prefixed to an adjective with a thematic suffix, as bicorniger, bicubitālis, bilongus, bipatens, and these are occasionally participial in form, as bicamerātus, biformātus. The Latin nouns, ending usually in -ium, are formed on the preceding adjectives, or possible ones of corresponding type, as biennium a space of two years, biennis lasting two years, biclīnium, *biclīnus.The prefix entered English in compounds, e.g. in bigame n. (compare post-classical Latin bigamus ), found c1300, bicorne n., c1420; bifront adj., biforked adj. occur late in 16th cent.; and from the 17th cent. onward, by a wide extension of the Latin analogy, especially in its later phases, bi- has been prefixed to any adjective conveniently indicating the thing or quality which is to be described as doubled or occurring twice, principally to those of Latin etymology, as in bi-angular adj. at sense 1a, bicavitary adj. at sense 1a, bicentral adj. at sense 1a, bivaulted adj. at sense 1a, bivoluminous adj. at sense 1a, but also to others as birainy adj. at sense 1a, bi-weekly adj. at sense 1d(b). In modern scientific terminology, adjectives in -ate , -ated are most frequently employed, as biauriculate adj. at biauricular adj., bicarinate adj., bilamellate adj., bipinnate adj., biunguiculate adj., bimaculated adj. at bimaculate adj. Derivatives; and the attributive use of nouns as adjectives tends to such modern forms as bichord adj. at sense 1a, biwhirl adj. at sense 1a. See also bin- prefix.