食或蚀，是一种天文事件，可以是一个天体进入另一个天体的影子，或是从观测者和另一个天体之间穿越，而造成暂时的屏蔽现象。食是一种朔望的型态。 “食”这个字最常用在日食－月球的影子掠过地球的表面，或月食－月球进入地球的阴影内。然而，这个字眼也可以用在地月系统之外的事件：例如，某行星进入它的一颗卫星所造成的影子内，或是卫星进入它的母行星的阴影内，或是一颗卫星进入另一颗卫星的影子内。在联星系统，当它的轨道平面和观察者横切时，也可能发生食的现象。

An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer. An eclipse is a type of syzygy.

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 Earth's shadow. However, it can also refer to such events beyond the Earth–Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its host planet, or a moon passing into the shadow of another moon. A binary star system can also produce eclipses if the plane of the orbit of its constituent stars intersects the observer's position.