The crescent moon is a phase of the moon that occurs when only a small portion of its surface is illuminated by the Sun. This shape resembles a thin, curved sliver and can be seen shortly after the new moon or just before the full moon. The crescent moon can appear in two forms: the waxing crescent, which grows larger, and the waning crescent, which shrinks. During the waxing crescent phase, the moon is visible in the western sky after sunset. In contrast, the waning crescent is seen in the eastern sky before sunrise. Both phases are part of the lunar cycle, which lasts about 29.5 days.