The slope of a passing through the and is the ratio of the vertical change to the horizontal change between the points. The variable is most commonly used to represent slope.
The words rise and run are sometimes used to describe the slope of a line, especially when the line is given graphically. Rise corresponds to and run corresponds to
This gives the following definition for the slope of a line.
Because the of a linear function is constant, any two points on the line can be used to find the slope – either algebraically with the or graphically as shown below.
The sign (positive or negative) of each distance corresponds to the direction of the movement between points. Moving to the right, the run is positive; moving to the left, the run is negative. Similarly, moving up yields a positive rise while moving down gives a negative rise.