\Bi-\ [L. bis twice, which in composition drops the -s, akin
to E. two. See {Bis-}, {Two}, and cf. {Di-}, {Dis-}.]
1. In most branches of science bi- in composition denotes
   two, twice, or doubly; as, bidentate, two-toothed;
   biternate, doubly ternate, etc.
2. (Chem.) 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.