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autumn equinox

autumn equinox

1 6.1
A time when day and night are about the same length that marks the start of autumn
  • noun
  • /ˈɔːtəm ˈiːkwɪnɒks/
translation icon : equinoccio de otoño
  • During the autumn equinox, day and night are of roughly equal length.

Examples

  • The decrease has been so gradual that we barely noticed the almost imperceptible shift, the subtle loss, until the autumn equinox when the light of the day and the dark of the night were of the same duration.

    Blog text (18)
  • If you do not find Zed's firstborn by the time of the autumn equinox, life in this world shall cease to exist.

  • Twice each year, at the spring and autumn equinox, the King selects a new victim - virgins.

  • The autumn equinox occurs on September 23, marking the start of autumn.

  • Many cultures celebrate the autumn equinox as a time of balance and harvest.

Synonyms

equinox
vsautumn equinox
15 7.4

A time twice a year when day and night are about the same length

refers only to the autumn occurrence rather than the twice yearly event
autumnal equinox
vsautumn equinox
1 7.4

The time in autumn when day and night are about equal

is the same astronomical moment but uses a different adjective form
fall equinox
vsautumn equinox
  • US
6.0

The time when day and night are almost the same length, marking the start of autumn in the Northern Hemisphere

is the same event but uses a different regional word for the season
September equinox
vsautumn equinox
  • Specialized
7.1

A time in late September when day and night are about equal, marking autumn north and spring south

marks the seasonal change without naming month or hemisphere
arrival of autumn
vsautumn equinox
2.0

The time when autumn begins

marks the astronomical moment that specifically signals the season start

Surface Forms

Morphology

autumn + equinox

The phrase is a straightforward noun–noun combination: an 'equinox' that occurs in 'autumn', so its meaning (the equinox marking the start of autumn with roughly equal day and night) is directly derivable from the constituents. This compositional pattern is cross-linguistically common (e.g. Spanish 'equinoccio de otoño'), so a learner who knows both words would readily understand it.

Etymology

Autumn equinox is the moment each year when the sun sits over Earth's middle line, so day and night are about the same length. People long ago used that clear change in light to mark the 'start of autumn', so the term means the first day of autumn.