Other forms: phases, phased, phasing
A phase is one stage in something that moves through stages, one after another. The planning phase of a project, the moon in its crescent phase, the phase your two-year-old is going through where every answer is no.
Phase is a verb too, and it takes in or out: a new rule is phased in over three years, an old model is phased out. 'It's just a phase' is what people say about behaviour they expect to pass — the black clothes, the six months of never speaking at dinner. In science a phase is a state of matter, so ice, water and steam are three phases of the same stuff. Two things that move together are in phase; when they drift apart, they are out of phase. And watch the spelling: phase is about time, faze is to unsettle someone, and nothing fazes her.
1nounphaseOne stage in a process or period of change, with others before and after it.
“The project moves into its testing phase next month.”
2verbbringTo bring something in, or take it out, in gradual stages.
“The company is phasing out plastic cups over the next year.”
3nounshapesOne of the shapes the moon shows as different parts of it are lit.
“He photographed every phase of the moon that winter.”
4nounstateA state in which matter exists, such as solid, liquid or gas.
“Water passes through three phases as it is heated.”
Too few real examples of this word to estimate which sense is commonest.
phase is a stage.
New Latin
phasis
English, today
phase
Borrowed from New Latin phasis. Compare phantasm and see face.
Etymology from Wiktionary, CC BY-SA