in Mathematics, is the cutting of one line, or plane, by another; or the point or line wherein two lines, or two planes, cut each other.

The mutual intersection of two planes is a right line. The centre of a circle is in the intersection of two diameters. The central point of a regular or irregular figure of four sides, is the point of intersection of the two diagonals.

The equinoxes happen when the sun is in the intersections of the equator and ecliptic.