In geography, a unit of angle measurement used to indicate the steepness of a slope. The grade of a slope is defined as the travelled vertical distance divided by the travelled forward distance, with the result multiplied by one hundred, i.e. $\text{grade}=\frac{\Delta y}{\Delta x}\times 100\%$. This result is then shown as a percentage. Also known by the shorthand expression 'rise over run'. A 100% grade indicates a slope with a 45 degree angle, while a vertical slope has an infinite grade. Unlike with degrees and radians, simple addition can not be used to add two grade values together.