- See under equinox (def. 1).
- the position of the sun at the time of the autumnal equinox.
- the time at which the sun crosses the plane of the equator away from the relevant hemisphere, making day and night of equal length. It occurs about Sept 23 in the N hemisphere (March 21 in the S hemisphere)
- astronomy
- the point, lying in the constellation Virgo, at which the sun's ecliptic intersects the celestial equator
- the time at which this occurs as the sun travels north to south (23 September)
