



(1) In architecture, a recess in a wall for a statue, a vase, built-in shelves, and similar objects. Niches are sometimes used to impart a sculptural quality to a wall.
(2) In geomorphology, a niche, or crater, is a cavity in the lower part of a protruding abrasion shoreline. It occurs as a result of wave erosion. As the niche becomes deeper, the weight of the bench of bedrock hanging over it increases. The bench finally breaks off and a cliff, an overhanging scarp, forms.
(3) In military science, a niche is a recess in the wall of a trench or communications passage. It is used to store ammunition and water and serves as protection from bullets, shell fragments, and mortar fire. It is also a shelter during bad weather. In loose soils, the walls and ceiling of the niche are faced with boards or any available material.