An endorheic basin (also endoreic basin) (from the Ancient Greek: ἔνδον, éndon, "within" and ῥεῖν, rheîn, "to flow") is a closed drainage basin that retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation. Such a basin may also be referred to as a closed or terminal basin or as an internal drainage system.