A burn is a watercourse (in size from a large stream to a small river).
The term burn is used in Scotland and England (especially North East England) and in parts of Ulster, Australia and New Zealand.
The cognate of burn in standard English is "bourn", "bourne", "borne", "born", which is retained in placenames like Bournemouth, King's Somborne, Holborn, Melbourne. A cognate in German is Born (contemp. Brunnen), meaning "well", "spring" or "source", which is retained in placenames like Paderborn in Germany. Both the English and German words derive from the Saxon "brunna".
Scots Gaelic has the word bùrn, also cognate, but which means "fresh water"; the actual Gaelic for a "burn" is allt (sometimes anglicised as "ault" or "auld" in placenames.)