If you are like me, you have a hard time remembering the exact definitions of the various items on the astronomical calendar. Fortunately, like other sciences, astronomical terms are mostly Latin in origin.
Look at the word: equi nox. The Latin adjective for “equal” is aequalis. And nox is the Latin word for “night.”
The autumnal equinox is the day of the year when the length of the night is equal to that of the day. It is that day when you say to yourself, “Omigosh, summer really is over!” And depression sets in because you start having to think about the oncoming winter.
It is to be distinguished from the solstice because the solstice is that time when the sun reaches either its highest or lowest points in the sky. Sol stice: The “standing” or “stopping” of the sun, from sol, meaning “sun,” and sistere, “standing still.” The course of the sun seems to stand still before rising or lowering in the sky.
Just one more practical benefit of knowing Latin.