n. & v.
1. a distinct period or stage in a process of change or development.
2 each of the aspects of the moon or a planet, according to the amount of its illumination, esp. the new moon, the first quarter, the last quarter, and the full moon.
3 Physics a stage in a periodically recurring sequence, esp. of alternating electric currents or light vibrations.
4 a difficult or unhappy period, esp. in adolescence.
5 a genetic or seasonal variety of an animal's coloration etc.
6 Chem. a distinct and homogeneous form of matter separated by its surface from other forms.
--v.tr. carry out (a programme etc.) in phases or stages.
Phrases and idioms:
in phase having the same phase at the same time. out of phase not in phase. phase in (or out) bring gradually into (or out of) use. phase rule Chem. a rule relating numbers of phases, constituents, and degrees of freedom. three-phase (of an electric generator, motor, etc.) designed to supply or use simultaneously three separate alternating currents of the same voltage, but with phases differing by a third of a period.
Etymology: F phase & f. earlier phasis f. Gk phasis appearance f. phaino phan- show