Either of two points on the celestial sphere at which the ecliptic intersects the celestial equator.
Either of the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal; the vernal equinox or the autumnal equinox.
[Middle English, from Old French equinoxe, from Medieval Latin aequinoxium, from Latin aequinoctium : aequi-, equi- + nox, noct-, night; see nekw-t- in Indo-European roots.]
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