equi·​nox | \ ˈē-kwə-ˌnäks How to pronounce equinox (audio) , ˈe- How to pronounce equinox (audio) \

Definition of equinox

1 : either of the two points on the celestial sphere where the celestial equator intersects the ecliptic
2 : either of the two times each year (as about March 21 and September 23) when the sun crosses the equator and day and night are everywhere on earth of approximately equal length

Equinox and the Seasons

Equinox descends from aequus, the Latin word for "equal" or "even," and nox, the Latin word for "night"—a fitting history for a word that describes days of the year when the daytime and nighttime are equal in length. In the northern hemisphere, the vernal equinox marks the first day of spring and occurs when the sun moves north across the equator. (Vernal comes from the Latin word ver, meaning "spring.") The autumnal equinox marks the first day of autumn in the northern hemisphere and occurs when the sun crosses the equator going south. In contrast, a solstice is either of the two moments in the year when the sun's apparent path is farthest north or south from the equator.

Examples of equinox in a Sentence

Recent Examples on the Web Fall has officially began, and Kendall Jenner rang in the equinox by dressing up in two long form-fitting dresses yesterday. Alyssa Bailey, ELLE, 23 Sep. 2022 The equinox is defined based on the position of the center of the sun. Jack Lee, San Francisco Chronicle, 23 Sep. 2022 The equinox will happen today, Sept. 22, at 8:03 p.m. CDT. Leada Gore | Lgore@al.com, al, 22 Sep. 2022 Technically, an equinox is not a day-long astronomical event. Justin Grieser, Washington Post, 21 Sep. 2022 In the Southern Hemisphere, this effect occurs around the spring equinox in either March or April, according to EarthSky. Megan Marples And Ashley Strickland, CNN, 9 Sep. 2022 With less than two weeks until the autumn equinox on Sept. 22, our temperatures seem to be sliding slowly toward autumn. Martin Weil, Washington Post, 10 Sep. 2022 The autumn equinox occurs on 23rd September, the same day the sun shifts into Libra. Lisa Stardust, refinery29.com, 28 Aug. 2022 This year, the equinox will take place on Wednesday at 3:20 p.m. After Wednesday, days will start becoming shorter than nights. Rashika Jaipuriar, The Indianapolis Star, 21 Sep. 2021 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'equinox.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of equinox

14th century, in the meaning defined at sense 1

History and Etymology for equinox

Middle English, from Anglo-French or Medieval Latin; Anglo-French equinocce, from Medieval Latin equinoxium, alteration of Latin aequinoctium, from aequi- equi- + noct-, nox night — more at night

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equinoctial year



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Last Updated

27 Sep 2022

Cite this Entry

“Equinox.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/equinox. Accessed 6 Oct. 2022.

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More Definitions for equinox


equi·​nox | \ ˈē-kwə-ˌnäks How to pronounce equinox (audio) , ˈe-kwə- \

Kids Definition of equinox

: either of the two times each year (as in spring around March 21 and in fall around September 23) when the sun's center crosses the equator and day and night are everywhere of equal length

More from Merriam-Webster on equinox

Nglish: Translation of equinox for Spanish Speakers

Britannica English: Translation of equinox for Arabic Speakers

Britannica.com: Encyclopedia article about equinox


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