conterminous

Conterminous is an adjective used in geography and political geography to describe areas that share a common boundary or are physically connected along a border. The term derives from Latin roots con- meaning together and terminus meaning end or boundary, conveying the sense of ends meeting at a border.

The phrase is most familiar in reference to the United States, with the conterminous United States describing the 48 adjoining states plus the District of Columbia that lie on the North American continent between Canada and Mexico. Alaska and Hawaii are not conterminous with the continental United States because they are separated by ocean. Beyond this, conterminous can be used to denote any regions, countries, or administrative divisions that touch along a boundary, although such usage is more common in formal or technical contexts or in cartography.

Conterminous is often treated as synonymous with contiguous in everyday language, since both imply adjacency. However, conterminous emphasizes the existence of a shared boundary, while contiguous may simply indicate physical proximity or direct contact. In practice, the choice between terms can depend on the specificity of the boundary relationship and the conventions of a given field or document.