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

In an email, Dr. Nixon said his team was particularly excited to see what would happen in 2025, when Titan would reach its northern autumnal equinox.

From New York Times • Dec. 5, 2022

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

Astronomically, in the northern hemisphere, it begins at the autumnal equinox, when the sun enters Libra, 22d September, and ends at the winter solstice, when the sun enters Capricorn, 21st December.—adj.

From Chambers's Twentieth Century Dictionary (part 1 of 4: A-D) by Various