phase

Concise Oxford English Dictionary © 2008 Oxford University Press:
phase /feɪz/

▶noun

• 1 a distinct period or stage in a process of change or development.

  ■ each of the aspects of the moon or a planet, according to the amount of its illumination.

• 2 Zoology a genetic or seasonal variety of an animal's coloration.

• 3 Chemistry a distinct and homogeneous form of matter separated by its surface from other forms.

• 4 Physics the relationship in time between the cycles of an oscillating or repeating system and a fixed reference point or a different system.

▶verb

• 1 carry out in gradual stages.

  ■ (phase something in/out) introduce something into (or withdraw something from) use in gradual stages.

• 2 apply phasing to (an electronic musical instrument).

• 3 Physics adjust the phase of (something), especially so as to synchronize it with something else.

– phrases
in (or out of) phase

• 1 in (or out of) synchrony or harmony.

• 2 Physics having or in the same (or different) phase or stage of variation.

– origin C19: from Fr., based on Gk phasis ‘appearance’.