grade (Geography Dictionary)

grade : Also slope, incline, gradient, pitch, rise, or mainfall.

A physical surface that is inclined with respect to the horizontal, or the angle between that surface and the horizontal, typically expressed in degrees, or calculated as a ratio of “rise” (vertical distance) to “run” (horizontal distance) and expressed as a fraction or percentage; a larger number indicates a steeper incline. The term “grade” is often used to describe the incline of man-made surfaces such as roads and the roofs of buildings, whereas the term “slope” is more commonly used to describe natural surfaces such as the sides of hills or mountains or the beds and banks of watercourses.