The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day are approximately equally long. It may be better understood to mean that +L and -L north and south of the Equator experience nights of equal length.
An equinox occurs twice a year, when the tilt of the axis is inclined neither away from nor towards the the center of the Sun being in the same plane as the Earth's
At an equinox, the Sun is at one of two opposite points on the where the (i.e. declination 0) and intersect. These points of intersection are called equinoctial points: classically, the vernal point and the autumnal point. By extension, the term equinox may denote an equinoctial point.
For most locations on earth, there are two distinct identifiable days per year when the length of day and night are closest to being equal; those days are referred to as the "equiluxes" to distinguish them from the equinoxes. Equinoxes are points in time, but equiluxes are days. By convention, equiluxes are the days where sunrise and sunset are closest to being exactly 12 hours apart.
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