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equinox

/ˈiːkwɪnɑːks/

Either of two times of equal day and night

From Latin aequus (equal) + Latin nox (night).

noun
aequus
Latin
AI-inferred
aequus
“equal”; the first element of the compound
Latin
Verified
aequinoctium
Combined with nox to express equality of night and day

from Latin aequinoctium, usually in plural, dies aequinoctii "the equinoxes,"

+1 more source
nox
Proto-Indo-European
Verified
*nókʷts
reconstructed
“night”; reconstructed ancestor

from Proto-Indo-European *nókʷts (“night”)) + -ium (suffix forming abstract nouns). The Latin word, ultimately adopted...

Latin
AI-inferred
nox (genitive noctis)
“night”; its oblique form supplied noct- in compounds
Latin
Verified
aequinoctium
The night-related element in the compound

from Latin aequinoctium, usually in plural, dies aequinoctii "the equinoxes,"

+1 more source
Combined
Latin aequinoctium
aequus “equal” + nox “night” + -ium, literally an “equality of night”
Medieval Latin
Verified
equinoxium
“equality of night (and day)”

from Medieval Latin equinoxium "equality of night (and day),"

Old French
AI-inferred
equinoce, equinoxe
Borrowed astronomical term
Middle English
AI-inferred
equinox, equinoxe, equynox
A period when day and night are of equal length
Modern English
AI-inferred
equinox
A moment when the Sun crosses the celestial equator
Modern English
equinox
“

Twice a year—around 20 March and 23 September—the Sun appears to stand directly over Earth’s equator, creating the neat visual trick of day and night balancing on a cosmic set of scales. Romans called this an aequinoctium: aequus meant “equal,” while nox meant “night,” so the name is essentially “equal-night”—a compact bit of ancient astronomical bookkeeping. The night root reaches back to reconstructed Proto-Indo-European *nókʷts and is the distant cousin of English night, French nuit, and German Nacht. Before the Latin borrowing displaced it, Old English had the wonderfully plain compound efnniht, literally “even-night.” English later took the polished Latin route, leaving us with a word that sounds grand but still means, at heart, a night and a day trying to tie.

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