A Circle can
be cut into four equal sectors by two diameters at right angles.
Each of these quarters of the circle is called a quadrant.

Each of the four regions into which the x-axis and y-axis divide the
plane is also called a quadrant. A quarter of a plane, bounded by
two lines at right angles to one another.

For example, in Cartesian co-ordinates
the part of the plane with both x and y positive is a quadrant.