The occultation (obscuring) of one celestial body by another.

Solar and lunar eclipses take place at syzygies of the Sun, Earth, and Moon, when the three bodies are in a line. At a solar eclipse, the Moon blocks the view of the Sun as seen from the Earth. At a lunar eclipse, the Earth’s shadow falls on the Moon, darkening it, and can be seen from wherever on Earth the Moon is above the horizon.