In geophysical and ecological terms, a niche designates the relationship between a species and its area of inhabitation. The term is specifically used to describe a species' unique position both in terms of physical area, and as a set of characteristics that relate the species' biological and ecological functions to its geophysical environment.

Although not the subject of this article, the term niche is also used to describe a type of glacier (e.g., niche glacier) that forms inside an irregular recess on or within a mountainside.

Four distinct stages of niche theory development in biological ecology can be identified: (1) Joseph Grinnell's original formulation of niche (in 1917 and 1928) as a geophysical spatial unit; (2) Charles Elton's formulation (in 1927) of niche as a functional unit; (3) Gause's (1934) competitive exclusion principle; and (4) E. Evelyn Hutchinson's concept of multidimensional niche in the 1950s.

Although Darwin understood the idea of niche and a few...