Definition: A taxon is Endangered when the best available evidence indicates that it meets any of the \r\ncriteria A to E for Endangered, and it is therefore considered to be facing a very high risk of extinction in the wild.
Definition: Gravel is an environmental material which is composed of pieces of rock that are at least two millimeters (2mm) in its largest dimension and no more than 75 millimeters.
Definition: A lake which is formed when a wide meander from a stream or a river is cut off to form a lake. They are called oxbow lakes due to the distinctive curved shape that results from this process.
Definition: A shallow stretch of a river or stream, where the current is above the average stream velocity and where the water forms small rippled waves as a result. It often consists of a rocky bed of gravels or other small stones.
Comment: "Large" is ambiguous. For details on "Large rivers" (e.g. the Mekong river) see http://worldwildlife.org/biomes/large-river-ecosystems This class will be replaced with a less ambiguous class.
