equinox

Definition

One of two times in the year (one in March and the other in September) when the length of the day and the night are equal, which occurs when the sun is directly overhead at the equator; this marks the beginning of spring in one hemisphere and autumn in the other.

Etymology

PIE word *nókʷts From Middle English equinox, equinoxe, equynox (“one of the two periods in the year when the day and night are of equal length, equinox; either the zodiac sign Aries or Libra, in which the sun crosses the celestial equator”), from Old French equinoce, equinoxe (modern French équinoxe), or from its etymon Medieval Latin ēquinoxium, ēquinoctium, from Latin aequinoctium (“equinox”), from aequus (“equal”) + nox (“night”) (ultimately derived from Proto-Indo-European *nókʷts (“night”)) + -ium (suffix forming abstract nouns). The Latin word, ultimately adopted in Middle English and modern English, displaced Old English efnniht (modern English evennight). The rare alternative plural form equinoctes treats equinox as if it were a Latin word; the plural of Latin nox (“night”) is noctēs.

Example Sentences

• "[T]he Months of March and September, the tvvo Æquinoxes of Our year, are the moſt vvindy and tempeſtuous, the moſt unſettled and unequable of Seaſons in moſt Countries of the VVorld."
• "The four grand and ſolemn Bardic days are, of ancient uſage, the tvvo equinoxes, and the tvvo ſolſtices; the nevv and full moons are alſo, ſubordinately, ſolemn Bardic days: […]"
• "[H]e [Milton] believed, his poetic vein only flowed from the autumnal to the vernal equinox; and, in his essay on Education, he doubts whether, in the fine days of spring, any study can be accomplished by young men."

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