Prairie Pothole Region in the context of Spring (season)

A pond is a small, still, land-based body of water formed by pooling inside a depression, either naturally or artificially. A pond is smaller than a lake and there are no official criteria distinguishing the two, although defining a pond to be less than 5 hectares (12 acres) in area, less than 5 metres (16 ft) in depth and with less than 30% of its area covered by emergent vegetation helps in distinguishing the ecology of ponds from those of lakes and wetlands.

Ponds can be created by a wide variety of natural processes (e.g. on floodplains as cutoff river channels, by glacial processes, by peatland formation, in coastal dune systems, by beavers). They can simply be isolated depressions (such as a kettle hole, vernal pool, prairie pothole, or simply natural undulations in undrained land) filled by runoff, groundwater, or precipitation, or all three of these. They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film.

In Earth science, a pothole is a smooth, bowl-shaped or cylindrical hollow, generally deeper than wide, found carved into the rocky bed of a watercourse. Other names used for riverine potholes are pot, (stream) kettle, giant's kettle, evorsion, hollow, rock mill, churn hole, eddy mill, and kolk. Although somewhat related to a pothole in origin, a plunge pool (or plunge basin or waterfall lake) is the deep depression in a stream bed at the base of a waterfall. It is created by the erosional forces of turbulence generated by water falling on rocks at a waterfall's base where the water impacts. Potholes are also sometimes referred to as swirlholes. This word was created to avoid confusion with an English term for a vertical or steeply inclined karstic shaft in limestone. However, given widespread usage of this term for a type of fluvial sculpted bedrock landform, pothole is preferred in usage to swirlhole.

The term pothole is also used to refer to other types of depressions and basins that differ in origin. For example, some authors refer to panholes found in the Colorado Plateau also as potholes. Other terms used for panholes are gnamma (Australia), opferkessel (German, roughly “sacrificial basin”), armchair hollows, weathering pans (or pits) and solution pans or solution pits. In another case, the term pothole is used to refer to a shallow depression, generally less than 10-acre (4.0 ha) in area that occurs between dunes or on subdued morainic relief on a prairie, as in Minnesota and the Dakotas, and often contains an intermittent pond or marsh that serves as a nesting place for waterfowl.