Definition of equinox in English:

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Pronunciation: /ˈiːkwɪnɒks/
Pronunciation: /ˈɛkwɪnɒks/


1The time or date (twice each year) at which the sun crosses the celestial equator, when day and night are of equal length (about 22 September and 20 March).
Example sentences
  • These nine nights occur on equinoxes or equal nights when the sun is vertically overhead at the equator or centre.
  • The lengths of the hours were equal around the equinoxes but the rest of the time they could vary considerably.
  • ‘An equinox is when night and day are equal,’ he said.
1.1 another term for equinoctial point.
Example sentences
  • A tropical year is the time it takes the sun to pass from one equinox, or tropic, to the same tropic or equinox again.
  • The position of the stars should not be related to the point of the equinox, that is to the position of the point which changes position in the course of time, but the position of the point of the equinox should be related to the sphere of stars.


Late Middle English: from Old French equinoxe or Latin aequinoctium, from aequi- 'equal' + nox, noct- 'night'.

  • night from Old English:

    Although an Old English word, night comes ultimately from the same root as Latin nox, the source of equinox (Late Middle English) and nocturnal (Late Middle English). Fortnight (Old English) is an Old English contraction of ‘fourteen nights’, and reflects an ancient Germanic custom of reckoning time by nights rather than days. The original night of the long knives was the legendary massacre of the Britons by the Saxon leader Hengist in 472. According to the 12th-century Welsh chronicler Geoffrey of Monmouth, the Saxons attended a meeting armed with long knives, and when a prearranged signal was given each Saxon drew his weapon and killed the Briton seated next to him. The phrase is now more commonly associated with the brutal suppression of the Brownshirts (a Nazi militia replaced by the SS) on Hitler's orders in 1934. It is also used of any decisive or ruthless sacking, in particular the occasion in 1962 when British Prime Minister Harold Macmillan dismissed a third of his cabinet at the same time. Nightmares are nothing to do with horses. In the Middle Ages a nightmare (Middle English) was thought of as an evil female spirit or monster that lay on sleeping people and suffocated them: the -mare part comes from Old English and meant ‘suffocating evil spirit’.

For editors and proofreaders

Line breaks: equi|nox

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