The term 'stage in a lunar cycle' can be summarized as a PHASE of the moon. The moon's cycle is divided into eight distinct phases, each lasting about three and a half days. The phases are new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. During each PHASE, the amount of light reflected from the moon's surface changes, creating the familiar shapes we see in the night sky.