Source : Webster's Revised Unabridged Dictionary (1913)

Phase \Phase\, n.; pl. {Phases}. [NL. phasis, Gr. ?, fr. ? to
   make to appear: cf. F. phase. See {Phenomenon}, {Phantom},
   and {Emphasis}.]
   1. That which is exhibited to the eye; the appearance which
      anything manifests, especially any one among different and
      varying appearances of the same object.

   2. Any appearance or aspect of an object of mental
      apprehension or view; as, the problem has many phases.

   3. (Astron.) A particular appearance or state in a regularly
      recurring cycle of changes with respect to quantity of
      illumination or form of enlightened disk; as, the phases
      of the moon or planets. See Illust. under {Moon}.

   4. (Physics) Any one point or portion in a recurring series
      of changes, as in the changes of motion of one of the
      particles constituting a wave or vibration; one portion of
      a series of such changes, in distinction from a contrasted
      portion, as the portion on one side of a position of
      equilibrium, in contrast with that on the opposite side.

Phasis \Pha"sis\, n.; pl. {Phases}. [NL.]
   See {Phase}. --Creech.