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 in area, less than 5 metres (16 ft) in depth and with less than 30% with 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, or they can simply be isolated depressions 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. The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Ponds are usually freshwater but may be brackish in nature. Saltwater pools, with a direct connection to the sea to maintain full salinity, may sometimes be called 'ponds' but these are normally regarded as part of the marine environment. They do not support fresh or brackish water-based organisms, and are rather tidal pools or lagoons.

അകത്തേക്കോ പുറത്തേക്കോ ഒഴുക്കില്ലാത്ത ഒറ്റപ്പെട്ട ചെറിയ ജലാശയങ്ങളെയാണ്‌ കുളം എന്നു പറയുന്നത്. പ്രധാനമായും മഴയാണ്‌ കുളങ്ങളിലെ ജലത്തിന്റെ സ്രോതസ്സ്. എന്നാൽ ഭൂഗർഭജലം ഒഴുകിയെത്തുന്ന കുളങ്ങളുമുണ്ട്. ക്ഷേത്രങ്ങൾ, മസ്ജിദുകൾ, ഗുരുദ്വാരകൾ എന്നിങ്ങനെ ആരാധനാലയങ്ങൾക്കൊപ്പം സാധാരണയായി കുളങ്ങളുണ്ടാകാറുണ്ട്.