equinox

[ ee-kwuh-noks, ek-wuh- ]

noun

1. the time when the sun crosses the plane of the earth's equator, making night and day of approximately equal length all over the earth and occurring about March 21 vernal equinox, or spring equinox and September 22 autumnal equinox.
2. either of the equinoctial points.

equinox

/ ˈɛkwɪˌnɒks; ˈiːkwɪˌnɒks /

noun

1. either of the two occasions, six months apart, when day and night are of equal length See vernal equinox autumnal equinox
2. another name for equinoctial point

equinox

/ ē′kwə-nŏks′ /

1. Either of the two points on the celestial sphere where the ecliptic (the apparent path of the Sun) crosses the celestial equator .
2. ◆ The point at which the Sun's path crosses the celestial equator moving from south to north is called the vernal equinox . The vernal equinox marks the zero point in both the equatorial and ecliptic coordinate systems; horizontal angular distances (right ascension in the equatorial system and celestial longitude in the ecliptic system) are measured eastward from this point. The vernal equinox is also known as the first point of Aries because when first devised some 2,000 years ago this point occurred at the beginning of Aries in the zodiac. Because of the westward precession of the equinoxes, the vernal equinox is now located at the beginning of Pisces.
3. ◆ The point at which the Sun's path crosses the celestial equator moving from north to south is called the autumnal equinox .
4. Either of the two corresponding moments of the year when the Sun is directly above the Earth's equator. The vernal equinox occurs on March 20 or 21 and the autumnal equinox on September 22 or 23, marking the beginning of spring and autumn, respectively, in the Northern Hemisphere (and the reverse in the Southern Hemisphere). The days on which an equinox falls have about equal periods of sunlight and darkness.
5. Compare solstice

equinox

1. The twice yearly times when the lengths of day and night are equal. At equinox, the sun is directly over the Earth 's equator . The vernal equinox occurs about March 22 and the autumnal equinox about September 21.

Word History and Origins

Origin of equinox¹

First recorded in 1350–1400; Middle English, from Medieval Latin equinoxium, for Latin aequinoctium “the time of equal days and nights” (equivalent to aequi- + noct- + -ium ); equi-, nocti-, -ium

Word History and Origins

Origin of equinox¹

C14: from Medieval Latin equinoxium, changed from Latin aequinoctium, from aequi- equi- + nox night

Example Sentences

Autumn equinox 2024: When is it?

From BBC

The automaker’s fortunes might improve in the months ahead, however, with the recent launch of two new crossovers, the Equinox EV and the Blazer EV.

From Los Angeles Times

Even traditional gyms like Equinox are now offering a $40,000-a-year concierge membership that includes sleep coaching, personal training, massage therapy and nutrition advice.

From Los Angeles Times

Rain warnings were in place over the weekend as summer officially drew to a close following the autumn equinox on Sunday afternoon.

From BBC

Astronomical autumn begins on Sunday, with the equinox occuring around lunchtime and, right on cue, the weather will start feeling more autumnal in the week ahead.

From BBC