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Pronunciation: bās


  1. The lower part or bottom; the part of a pyramidal or conic structure opposite the apex (heart); the foundation.
  2. pharmacy the chief ingredient of a mixture.
  3. chemistry an electropositive element (cation) that unites with an anion to form a salt; a compound ionizing to yield hydroxyl ion.
  4. Nitrogen-containing organic compounds (purines, pyrimidines, amines, alkaloids, and ptomaines) that act as Brønsted bases.
  5. Cations, or substances forming cations.
  6. A substance the pH of which is over 7.0, in contrast to an acid.

Synonym(s): basisTA, basement1

[L. and G. basis]

See Also: Brønsted base, Lewis base
