1 the time or date (twice each year) at which the sun crosses the celestial equator, when day and night are of equal length.
2 = equinoctial point.
autumn (or autumnal) equinox about 22 Sept. spring (or vernal) equinox about 20 March.
ME f. OF equinoxe or med.L equinoxium for L aequinoctium (as EQUI-, nox noctis night)
aphelion, apogee, astronomical longitude, autumnal equinox, celestial equator, celestial longitude, celestial meridian, circle, colures, ecliptic, equator, equinoctial, equinoctial circle, equinoctial colure, galactic longitude, geocentric longitude, geodetic longitude, great circle, heliocentric longitude, longitude, meridian, orbit, perigee, perihelion, period, small circle, solstice, solstitial colure, summer solstice, trajectory, vernal equinox, winter solstice, zodiac, zone