autumnal equinox

American  

[aw-tuhm-nl ee-kwuh-noks, ek-wuh-noks] / ɔˈtʌm nl ˈi kwəˌnɒks, ˈɛk wəˌnɒks /

noun

1. equinox1

2. Also called autumnal point.  the position of the sun at the time of the autumnal equinox.

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autumnal equinox British  

noun

1. 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)

2. astronomy

   1. the point, lying in the constellation Virgo, at which the sun's ecliptic intersects the celestial equator

   2. the time at which this occurs as the sun travels north to south (23 September)

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autumnal equinox Scientific  

/ ô-tŭm′nəl /

1. See under equinox

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Etymology

Origin of autumnal equinox

First recorded in 1670–80

Example Sentences

Or, as we say north of the equator, happy autumnal equinox!

From Scientific American • Sep. 22, 2023

On September 23, 2023, the autumnal equinox will signal the coming of fall for the Northern Hemisphere.

From National Geographic • Sep. 21, 2023

The Fremont Arts Council celebrates the autumnal equinox with this illuminating lantern parade around Green Lake at 6 p.m.

From Seattle Times • Sep. 22, 2022

The crop was planted unusually late, after the autumnal equinox, the traditional last day of planting in the area.

From New York Times • May 11, 2022

The sun enters Aries, at the time of the vernal equinox; Cancer, at the summer solstice; Libra, at the autumnal equinox; and Capricornus, at the winter solstice.

From Conversations on Natural Philosophy, in which the Elements of that Science are Familiarly Explained by Jones, Thomas P.