(logic) The division of a class into two disjoint subclasses that are together comprehensive, as the division of man into white and not white.
(biology) The division of a genus into two species; a division into two subordinate parts.
(astronomy) A phase of the moon when it appears half lit and half dark, as at the quadratures.
(biology) Division and subdivision; bifurcation, as of a stem of a plant or a vein of the body into two parts as it proceeds from its origin; often successive.
