equinox

noun equi·nox \ˈē-kwə-ˌnäks, ˈe-\

: a day when day and night are the same length

Full Definition of EQUINOX

: either of the two points on the celestial sphere where the celestial equator intersects the ecliptic

: 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

See equinox defined for English-language learners

See equinox defined for kids

Origin of EQUINOX

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

Other Astronomy Terms

gibbous, nadir, nebulous, penumbra, retrograde, sidereal, syzygy, wane, wax, zenith

Rhymes with EQUINOX

arctic fox, ballot box, bobby socks, chatterbox, chicken pox, dealing box, ditty box, flying fox, journal box, miter box, music box, orthodox, paradox, pepperbox, pillar-box, ready box, sentry box, service box, shadowbox, shadow box, silver fox, Skinner box, stuffing box, tinderbox, window box, witness-box

EQUINOX Defined for Kids

equinox

noun equi·nox \ˈē-kwə-ˌnäks, ˈe-kwə-\

Definition of EQUINOX for Kids

: either of the two times each year (as in spring around March 21 and in fall around September 23) when the sun's center crosses the equator and day and night are everywhere of equal length