n a particular geographical region of indefinite boundary (usually serving some special purpose or distinguished by its people or culture or geography)
n a subject of study
n a part of an animal that has a special function or is supplied by a given artery or nerve
n a particular environment or walk of life
n a part of a structure having some specific characteristic or function
n the extent of a 2-dimensional surface enclosed within a boundary
n. 区域, 领域；面积（area的复数形式）