equinox

noun

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

Did you know?

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 In the Northern Hemisphere, the autumnal equinox is Sunday, Sept. 22, marking the start of the fall season. Emily Deletter, USA TODAY, 20 Oct. 2024 The Great Sphinx of Egypt – built some 5,000 years ago – also directly faces the rising sun on the spring (vernal) and autumn equinoxes. New Atlas, 7 Oct. 2024 The Earth is expected to experience a geomagnetic storm this week following the autumnal equinox. Timothy H.j. Nerozzi Fox News, Fox News, 24 Sep. 2024 The equinox was actually Sunday morning, so Sunday still had that last whiff of summer. Erik Kain, Forbes, 23 Sep. 2024 See all Example Sentences for equinox 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'equinox.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

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

First Known Use

14th century, in the meaning defined at sense 1

Time Traveler
The first known use of equinox was in the 14th century

Podcast

Dictionary Entries Near equinox

Cite this Entry

“Equinox.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/equinox. Accessed 31 Oct. 2024.

Kids Definition

equinox

noun
: either of the two times each year about March 21 and September 23 when the sun appears overhead at the equator and day and night are everywhere of equal length
Etymology

Latin equinoxium (same meaning), derived from earlier Latin aequi- "equal" and noct-, nox "night" — related to nocturnal

More from Merriam-Webster on equinox

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!