- In most branches of science bi- in composition denotes two,
twice, or doubly; as, bidentate, two-toothed; biternate, doubly
ternate, etc. - 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.
Bi-level purge valve Bi-level purge valve in an evaporative emissions system, a valve that limits the flow of vapor from the charcoal canister to the intake during
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