What does a lunation represent?

A lunation specifically refers to the lunar month, which is the mean duration of the moon's full cycle around the Earth. This typically lasts about 29.5 days and encompasses the varying phases of the moon—new moon, first quarter, full moon, and last quarter.

In a lunation, one can observe how the position of the moon relative to the Earth and the sun results in the changing appearance of the moon from Earth, which is integral for understanding lunar calendars and the timing of various cultural or astronomical events.

The other options describe different astronomical or natural phenomena. The rotation of the Earth on its axis pertains to a day, the cycle of the tides is influenced by gravitational interactions, and the phases of the sun are related to solar cycles rather than lunar changes. Thus, the definition centered around the moon's relationship to Earth and its orbit distinctly aligns with the concept of lunation.