a part of a structure having some specific characteristic or function | a small yellowish central area of the retina that is rich in cones and that mediates clear detailed vision |
the extent of a 2-dimensional surface enclosed within a boundary | a patch of skin that is discolored but not usually elevated; caused by various diseases |
a part of an animal that has a special function or is supplied by a given artery or nerve | a cooler darker spot appearing periodically on the sun's photosphere; associated with a strong magnetic field |
a subject of study | |
a particular geographical region of indefinite boundary (usually serving some special purpose or distinguished by its people or culture or geography) | |
a particular environment or walk of life | |