Slope
The direction or slant of a line in the plane is determined by its slope. The slope of the line that passes through the two distinct points (x1,y1) and (x2,y2) is given by m = (y2-y1) / (x2-x1), provided x2 is not equal to x1. If x2=x1, the line is vertical and the slope is not defined (In this case, the slope is sometimes said to be infinite).