bi-

1. a combining form meaning “twice,” “two,” used in the formation of compound words: bifacial; bifarious.

1. variant of bio-, especially before a vowel: biopsy.

combining form

1. two; having twobifocal
2. occurring every two; lasting for twobiennial
3. on both sides, surfaces, directions, etcbilateral
4. occurring twice duringbiweekly
5. 1. denoting an organic compound containing two identical cyclic hydrocarbon systemsbiphenyl
   2. (rare in technical usage) indicating an acid salt of a dibasic acidsodium bicarbonate
   3. (not in technical usage) equivalent of di- 1 (def. 2a)

combining form

1. a variant of bio-

word-forming element meaning “two, twice, double, doubly, once every two,” etc., from Latin bi- “twice, double,” from Old Latin dvi- (cognate with Sanskrit dvi-, Greek di-, Old English twi- “twice, double”), from PIE root *dwo- “two.” Nativized from 16c. Occasionally bin- before vowels; this form originated in French, not Latin, and might be partly based on or influenced by Latin bini “twofold” (see binary).