A distinct period or stage in a series of events or a process of change or development.

"the final phases of the war"

synonyms: stage, period, chapter, episode, part, step, point, time, juncture

"the final phase of the election campaign"

2.

each of the aspects of the moon or a planet, according to the amount of its illumination, especially the new moon, the first quarter, the full moon, and the last quarter.

synonyms: aspect, shape, form, appearance, state, condition

"the phases of the moon"