What is a region in math?

In a Cartesian coordinate system, the plane is divided into four quarters, or regions, by two axis which are vertical to each other. These axis are better known as the X and Y axis.

The regions are designated I, II, III, IV starting from the positive, positive region (both values of X and Y are positive) - region I, clockwise.

Region II is the region where coordinates are below the X-axis (negative) and right of the Y-axis (positive).

Region III is the region where both X and Y values are negative.

Region IV is the region where X values are positive and Y values are negative.