equinox

باللغة العربية: اِعْتِدَال

1. One of two times in the year (one in March and the other in September) when the length of the day and the night are equal, which occurs when the sun is directly overhead at the equator; this marks the beginning of spring in one hemisphere and autumn in the other.
2. The circumstance of a twenty-four hour time period having the day and night of equal length. (figuratively)
3. One of the two points in space where the apparent path of the Sun intersects with the equatorial plane of the Earth.

الجمع equinoxes