Definition:Equinox/Autumnal

Definition
The autumnal equinox is the equinox at which the sun crosses the celestial equator from north to south.

In the northern hemisphere this crossing occurs sometime around $23$ September.

Also known as
The autumnal equinox is also known as the September equinox or the fall equinox.

The term southward equinox can also be seen in contexts requiring hemisphere neutrality.

Also see

 * Definition:Vernal Equinox