Eclipse eclipse is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is derived from the ancient Greek noun (''''' Solar System, it forms a type of syzygy—gravitational system along a straight line. The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. However, it can also refer to such events beyond the Ea