Equinox

Part of speech: noun

Pronunciation: /ˈɛkwɪnɒks/

Definitions

1. A specific time each year when sunlight and darkness are nearly balanced equally during the day and night due to the sun's position relative to the earth's equator
2. A celestial event happening biannually when the hours of daylight and nighttime are roughly the same, indicating the transition between seasons
3. A biannual astronomical event characterized by the equal duration of day and night, marking seasonal changes in relation to the Earth's tilt and orbit around the sun

Etymology: "Equinox" is a Latin compound that English borrowed as a clerical and astronomical term, and it pushed out an older native word. Before it, Old English speakers called the same moment "efnniht," meaning "even night," a name that described the balance of light and dark in plain terms. The Latin "aequinoctium" was built from "aequus," meaning "equal," and "nox," meaning "night," with the suffix "-ium" that turns such pairs into abstract nouns. Medieval Latin then reshaped it as "aequinoctium" and "equinoctium," and Middle English took it from Old French "equinoce" and "equinoxe." The English word did not simply replace "efnniht" overnight. Middle English texts used "equinox" for both the day when night and day were equal and for the zodiac signs Aries and Libra, where the sun crosses the celestial equator. Modern English keeps the Latin form, and the older "evennight" survives only in dictionaries as a reminder of the native alternative.

Synonyms: solstice, season change, daylight equal, INVALID, INVALID