1. Either of the two points of intersection of the sun's apparent annual path and the plane of the earth's equator, that is, a point of intersection of the ecliptic and the celestial equator. 2. Popularly, the time at which the sun passes directly above the equator; the “time of the equinox. ”

In northern latitudes the vernal equinox falls on or about 21 March, and the autumnal equinox on or about 22 September. These dates are reversed in the Southern Hemisphere. Compare solstice.