A tumulus (plural tumuli) is a mound of earth and stones raised over a grave or graves. Tumuli are also known as barrows, burial mounds or kurgans, and may be found throughout much of the world. A cairn, which is a mound of stones built for various purposes, may also originally have been a tumulus.
Tumuli are often categorised according to their external apparent shape. In this respect, a long barrow is a long tumulus, usually constructed on top of several burials, such as passage graves. A round barrow is a round tumulus, also commonly constructed on top of burials. The internal structure and architecture of both long and round barrows has a broad range; the categorization only refers to the external apparent shape.
The word tumulus is Latin for 'mound' or 'small hill', which is derived from the Proto-Indo-European root *teuh2- with extended zero grade *tum-, 'to bulge, swell' also found in tomb, tumor, tumescent, thumb, thigh, and thousand.