lough

Lough is a term used primarily in Ireland to denote a lake or inland body of standing water, typically freshwater, though some loughs have brackish or tidal influence. The spelling differs from loch, used in Scotland, though both derive from Gaelic words for lake. The term is widely used in Ireland, especially in the names of places and towns.

Loughs are formed by a variety of processes, including glacial sculpting, tectonic activity, and riverine dynamics. They range from small ponds to large lakes and are often part of wider river catchments with inflow from streams and groundwater. Some coastal loughs function as estuarine inlets connected to the sea, and salinity can vary seasonally and with tidal exchange.

They provide important habitats for aquatic life, including freshwater fish such as salmon and trout, as well as water birds and diverse aquatic plants. Many loughs are designated as protected areas or nature reserves and are managed for conservation and recreation. Human use is diverse, including drinking water supply, fishing, boating, tourism, and local industry; nutrient loading, invasive species, and hydrological changes may threaten their ecology.

Notable examples include Lough Neagh, the largest lake by area in the British Isles; Lough Erne, in County Fermanagh, consisting of two main basins; Lough Corrib, a large lake in the west of Ireland; and Lough Derg on the River Shannon, a major lake used for recreation and navigation. Lough Ree on the River Shannon is another prominent example.