adit

thumb|Gated entrance of an abandoned adit near Medford, Oregon, United States

An adit (from Latin aditus, entrance) or stulm is a horizontal or nearly horizontal passage to an underground mine. Miners can use adits for access, drainage, ventilation, and extracting minerals at the lowest convenient level. Adits are also used to explore for mineral veins. Although most strongly associated with mining, the term adit is sometimes also used in the context of underground excavation for non-mining purposes; for example, to refer to smaller underground passageways excavated for underground metro systems, to provide pedestrian access to stations (pedestrian adits), and for access required during construction (construction adits).