Lunar phase

The lunar phase or Moon phase is the shape of the Moon's directly sunlit portion as viewed from Earth. The lunar phases gradually change over a synodic month (about 29.53 days) as the Moon's orbital positions around Earth and Earth around the Sun shift. The visible side of the moon is variously sunlit, depending on the position of the Moon in its orbit. Thus, this face's sunlit portion can vary from 0% (at new moon) to 100% (at full moon). Each of the four "intermediate" lunar phases (see below) is approximately 7.4 days, with slight variation due to the Moon's orbit's elliptical shape.

The lunar phases and librations in 2021 as viewed from the Northern Hemisphere at hourly intervals, with titles and supplemental graphics
The lunar phases and librations in 2021 as viewed from the Southern Hemisphere at hourly intervals, with titles and supplemental graphics
A full Moon sets behind San Gorgonio Mountain in California on a midsummer's morning.