Definition: A landform that extends above the surrounding terrain in a limited area. A mountain is generally steeper than a hill, but there is no universally accepted standard definition for the height of a mountain or a hill although a mountain usually has an identifiable summit and a local relief of more than 300m.
Definition: A narrow and shallow incision into soil resulting from erosion by overland flow that has been focused into a thin thread by soil surface roughness. Rilling, the process of rill formation, is common on agricultural land and unvegetated ground.
