Slope – Wikipedia

The slope of a line in the plane containing the x and y axes is generally represented by the letter m, and is defined as the change in the y coordinate divided by the corresponding change in the x coordinate, between two distinct points on the line. This is described by the following equation: = = =. (The Greek letter delta, Δ, is commonly used in mathematics to mean “difference” or “change”.)

: https://en.wikipedia.org/wiki/Slope