Quadrant
A quadrant is one of the 4 parts of a cartesian coordinate grid. The grid is made by crossing two number lines that intersect at zero (0,0) (the origin) to make a plane. The horizontal axis is the X axis and the vertical axis is the Y axis. They are numbered with roman numerals to denote the 4 parts of the grid like this:
Quadrant II: X is negative and Y is positive

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Quadrant I: Both X and Y are positive 
Quadrant III: X and Y are both negative

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Quadrant IV: X is positive and Y is negative

For an explanation of cartesian coordinates and quadrants see the notes on cartesian coordinates.
