Autumnal Equinox,
one of two times of year when the Sun’s position
makes day and night of nearly equal length in all
parts of the Earth. The autumnal equinox, which
usually occurs on September 22 or 23, marks the
beginning of the fall season in the Northern
Hemisphere.

Definition: Equinox
e.qui.nox

( plural e.qui.nox.es )

noun

1. time of equal day and night: either of the two
annual crossings of the equator by the Sun, once
in each direction, when the length of day and night
are approximately equal everywhere on Earth. The
equinoxes occur around March 21 and September
23.

2. astronomy
Same as equinoctial point

(14th century. Directly or via French - Latin
aequinoctium "equal night" - nox "night")

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"Autumnal Equinox,"
Microsoft® Encarta® Online Encyclopedia 2005
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