equinox
equinox Lexical Profile
equinox Game Scores & Validity
• noun
Either of the two times each year (around March 20 and September 22) when the sun crosses the plane of the Earth's equator, making day and night of approximately equal length all over the Earth.
"The autumn equinox marks the official astronomical transition from summer to fall in the Northern Hemisphere."
Either of the two points on the celestial sphere where the celestial equator intersects the ecliptic.
"Astronomers measure right ascension eastward along the celestial equator starting from the vernal equinox."
Word Nuance & Usage
Do not confuse with 'solstice': an equinox occurs twice a year (in March and September) when day and night are approximately equal in length, whereas a solstice occurs in June and December when the sun reaches its highest or lowest excursion relative to the celestial equator, resulting in the longest or shortest day of the year.
• Nearby Words
Word Origin & Etymology
Borrowed in Middle English via Old French from Medieval Latin 'aequinoxium', an alteration of Classical Latin 'aequinoctium', formed from 'aequus' (equal) and 'nox, noctis' (night).