The steepness of a hill is called a slope. The same goes for the steepness of a line. The slope is defined a s the ratio of the vertical change between two points, the rise, to the horizontal change between the same two points, the run. slope=riserun=changeinychangei
The slope of a line is usually represented by the letter m. (x1, y1) represents the first point whereas (x2, y2) represents the second point.