equinox

Meanings

1. 1
   noun

   either of the two times each year when the Sun crosses the celestial equator and day and night are approximately equal in length

   In the Southern Hemisphere, the September equinox marks the beginning of spring.

2. 2
   noun

   either of the two points where the celestial equator intersects the ecliptic

   Astronomers use the March equinox as a reference point in celestial coordinates.

From Middle English equinox, through Old French and Medieval Latin from Latin aequinoctium, 'equinox,' formed from aequus, 'equal,' + nox, noctis, 'night.' The name refers to the near equality of daylight and darkness.

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