Bi-

CIDE DICTIONARY

Bi-,  [L. bis twice, which in composition drops the -s, akin to E. two. See Bis-, Two, and cf. Di-, Dis-.].

•  In most branches of science bi- in composition denotes two, twice, or doubly; as, bidentate, two-toothed; biternate, doubly ternate, etc.  [1913 Webster]
•  In the composition of chemical names bi- denotes two atoms, parts, or equivalents of that constituent to the name of which it is prefixed, to one of the other component, or that such constituent is present in double the ordinary proportion; as, bichromate, bisulphide. Be- and di- are often used interchangeably.  [1913 Webster]

OXFORD DICTIONARY

Bi-, comb. form (often bin- before a vowel) forming nouns and adjectives meaning:
1 having two; a thing having two (bilateral; binaural; biplane).
2 a occurring twice in every one or once in every two (bi-weekly). b lasting for two (biennial).
3 doubly; in two ways (biconcave).
4 Chem. a substance having a double proportion of the acid etc. indicated by the simple word (bicarbonate).
5 Bot. & Zool. (of division and subdivision) twice over (bipinnate).

Etymology

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