What does coterminous mean?
Coterminous is a formal adjective describing things that share exactly the same boundaries or occupy precisely the same span of time. It is used most often in legal, political, and administrative contexts: a school district may be coterminous with a city's limits, or a chief executive's contract may be coterminous with a company's fiscal year. The word typically takes the preposition 'with', as in 'the diocese is coterminous with the county'. Its force lies in exactness — where 'contiguous' means merely touching or adjoining, coterminous asserts perfect coincidence of edges or endpoints. Derived from Latin roots meaning 'together' and 'boundary', it entered English in the early nineteenth century alongside its now rarer twin 'conterminous'. Though it rarely appears in casual conversation, it is indispensable in law, geography, and governance, wherever precision about matching limits matters more than everyday phrasing.
adjectiveHaving the same boundaries or extent in space or time; coinciding exactly in scope or duration. Often used of territories, jurisdictions, terms of office, or periods that begin and end together.
- (Of spatial areas such as territories or jurisdictions) having exactly the same boundaries.
- (Of time periods, terms, or durations) beginning and ending at the same time; coinciding in duration.
- (Figuratively) coextensive in scope or range; covering exactly the same area of concern.
"The new school district was coterminous with the city limits, simplifying tax collection."
"In many American states, the boundaries of congressional districts are deliberately kept coterminous with existing county lines."
"Her tenure as editor-in-chief was coterminous with the magazine's most turbulent decade."
Two countries can be neighbours without being coterminous — but when your city limits and your county lines are drawn on top of each other, lawyers call it coterminous, and everyone else calls it a paperwork miracle.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coterminous
Coterminous derives from the Latin prefix co- ('together') combined with terminus ('boundary, limit'), via the verb terminare ('to bound or limit'). It emerged in English in the early nineteenth century as a learned formation, appearing alongside the slightly earlier variant 'conterminous'. The same Latin root terminus gives English words such as terminal, terminate, and exterminate. Both spellings remain acceptable, though coterminous has become the dominant form.
Related word forms
How coterminous is actually used
Coterminous is a formal word found chiefly in legal, governmental, academic, and technical writing. It is almost always followed by 'with' (e.g., 'coterminous with the parish boundary'). The variant spelling 'conterminous' is older but now less frequent, particularly in British English. Avoid using it loosely to mean simply 'adjacent' — precise boundary-matching is the point.
Easily confused with coterminous
Conterminous is a near-identical synonym meaning the same thing; both derive from the same Latin roots, and the two are largely interchangeable, with 'coterminous' now the more common form.
Contiguous means merely touching or adjoining (sharing a border), whereas coterminous means sharing the exact same boundaries or extent.