See Also:

bi- (iou)



bi- prefix. before a vowel (cf. BIS-).
[Latin (earlier dui-, cogn. with Greek DI-2, Sanskrit dvi-) = twice, doubly, having two, two-.]
Used in words adopted from Latin and in English formations modelled on these, and as a productive prefix, forming (a) adjectives (and corresp. adverbs etc.) from adjectives or adverbs, with the senses 'having or involving two', as bicoloured, bilateral, bimanual, binaural, 'doubly, in two ways', as biconcave, bipyramidal, (Botany & Zoology) 'twice over, divided into similarly divided parts', as bipinnate, 'lasting for two, appearing every two', or (with resulting ambiguity) 'appearing twice in', as biannual, biennial, bimonthly, and 'joining two', as biparietal; (b) nouns from nouns with the sense 'double, thing having two', as bilayer, biplane; in Chemistry forming names of salts having a doubled proportion of acid to base radicals, as bicarbonate, binoxalate, bisulphate, or of molecules formed from two identical radicals, as biphenyl.