1. Each of the successive aspects or stages in any course of change or development.
2. The view that anything presents to the eye, or any one of varying distinctive manifestations of an object.
3. An aspect in the cycle of changing form or quantity of illumination of the moon or of a planet.
4. A uniform bounded portion of matter that is mechanically separable from a heterogeneous physico-chemical system.
5. The progress of a cyclic harmonic motion in relation to some standard point of reference (in time or space), usually expressed in angular measure, 360 degrees representing a full period or cycle in phase in or of the same phase.
6. One of the distinct stages in the reduction or division process of a cell and any characteristic or decisive stage in the growth, development, or life pattern of an organism.
7. A particular stage, or point, in a sequence through which time has advanced, measured from some arbitrary starting point.
8. Etymology: from French phase and from Modern Latin phases, plural of phasis, "phase" from Greek phainein, "to show, to appear".

To gradually make something happen: Tom was planning systematically to phase the development of a new house for his family.

A liquid extraction that has a lower concentration of material which is being extracted: Dr. Rogers and the chemists were excited with the results of the dilute phase of their newest chemical experiment.

A reference to certain insects during the period in which they are clustering in large numbers and are highly active: The agricultural students noticed that during the gregaria phase of the locusts life cycle, they were very noisy and moving around a great deal.