A sump is a low space that collects often undesirable liquids such as water or chemicals. It can also be an infiltration basin used to manage surface runoff water and recharge underground aquifers. A sump can refer to an area in a cave where an underground flow of water exits the cave into the earth. In addition, a sump can be a pit or reservoir serving as a drain or receptacle for liquids.

One common example of a sump is the lowest point in a basement, into which flows water that seeps in from outside. To prevent flooding and water damage, a sump pump can be used to move water from the sump to the outside of the house.

In an aquarium, a sump is a container of water placed below the main tank and is used as a filter, as well as a holding place of unsightly equipment such as heaters and protein skimmers. The main advantage of having a sump plumbed into an aquarium is the increase of water in the system, making it more stable and less prone to fluctuations of pH and salinity.

In mining, a sump is used to describe a hole made in the floor of a level in a working, in the direction of a lower level either for the purpose of testing the trend of an ore vein, or for the purpose of ventilation.

In summary, a sump is a low space that collects liquids, and it can have various applications such as managing surface runoff water, preventing flooding in basements, and filtering water in aquariums.