(διχοτομία, a division into two parts), in Astronomy, that phase of the moon in which it is bisected, or shows only half its disk. In this situation the moon is said to be in a quadrature aspect, or in its quadrature. The term is also used in botany to express a mode of branching by repeated bifurcation, as exemplified in the leaves of ferns.

**DICOTYLEDONOUS**, in Botany, a term applied to plants whose seeds have two lobes or cotyledons.