A hill is a landform that extends above the surrounding terrain. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit. The distinction between a hill and a mountain is unclear and largely subjective, but a hill is generally somewhat lower and less steep than a mountain. A hillock is a small hill. Other words include knoll and (in Scotland, Northern Ireland and northern England) its variant, knowe.
There are various specific names used to describe particular types of hill, based on appearance and method of formation. Many such names originated in one geographical region to describe a type of hill formation peculiar to that region, though the names are often adopted by geologists and used in a wider geographical context. These include:
- Drumlin – an elongated whale-shaped hill formed by glacial action.
- Butte – an isolated hill with steep sides and a small flat top, formed by weathering.
- Tor – a rock formation found on a hilltop; also used to refer to the hill itself.
- Puy – used to describe a conical volcanic hill.
- Pingo – a mound of earth-covered ice.