<P> In mathematics, the slope or gradient of a line is a number that describes both the direction and the steepness of the line . Slope is often denoted by the letter m; there is no clear answer to the question why the letter m is used for slope, but it might be from the "m for multiple" in the equation of a straight line "y = mx + b" or "y = mx + c". </P> <P> Slope is calculated by finding the ratio of the "vertical change" to the "horizontal change" between (any) two distinct points on a line . Sometimes the ratio is expressed as a quotient ("rise over run"), giving the same number for every two distinct points on the same line . A line that is decreasing has a negative "rise". The line may be practical - as set by a road surveyor, or in a diagram that models a road or a roof either as a description or as a plan . </P>

What is the term for how steep a line is in math