A cursus is an enormously elongated rectalinear earthwork enclosure whose length is over 250m and whose proportions are such that the long axis is more than ten times the short axis. The sides are usually defined by a bank and external ditch, but occasionally by a line of closely-set pits. The two long sides run roughly parallel, and may incorporate earlier monuments of other classes. The function of cursus is not known, although they are presumed to be ritual/ceremonial monuments. Cursus are of middle and late Neolithic date.
The recognition of cursus as field monuments often relies heavily on the results of aerial reconnaissance because most are heavily denuded and no longer survive as earthworks.
Cursus are sometimes confused with a variety of other classes of monument, particularly when incomplete. Long mortuary enclosures are one possible source of confusion, but these tend to be much shorter than cursus, generally less than 150m long whereas cursus are typically over 250m long. Other potential sources of confusion are bank barrows and avenues which can have ditches of equal length to short cursus, but which do not have closed ends like cursus. Roman roads, old field boundaries and ditched trackways have sometimes been incorrectly interpreted as cursus, but their true status is usually clear enough from close scrutiny of associations and minor details of form.