What does coextensive mean?
"Coextensive" is a formal adjective describing two things that have exactly the same extent, boundaries, or scope — nothing more and nothing less. A city's limits may be coextensive with its county's; in philosophy or law, one concept may be coextensive with another, meaning wherever one applies, the other applies too. The word is built from the Latin-derived elements "co-" (together) and "extensive," literally signifying "stretched out together." It appears almost exclusively in scholarly, legal, and technical contexts — discussions of jurisdiction, rights, definitions, and territories — and is nearly always paired with the preposition "with": "authority coextensive with the state's borders." Because it expresses exact equivalence of range rather than mere overlap, it is more precise than words like "similar" or "overlapping." For writers needing to assert that two domains coincide perfectly, "coextensive" is the standard, authoritative choice.
adjectiveHaving exactly the same extent, scope, or boundaries as something else; occupying precisely the same space or covering the same range.
- Having the same boundaries or spatial extent as something else.
- Having the same scope, range, or application as something else (e.g., a right coextensive with a duty).
"The city's administrative boundaries are coextensive with the county line."
"The parish and the school district are coextensive, covering precisely the same territory."
"In this theory, moral obligation is held to be coextensive with rational capacity."
Two things that are coextensive don't just overlap — they end at exactly the same point, which is why lawyers and philosophers love this word.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coextensive
The word "coextensive" derives from Latin roots: "co-" meaning "together" and "extensive" from the Latin "extensus," past participle of "extendere" ("to stretch out"). It entered English usage in the early modern period alongside other learned compounds formed with Latin prefixes on Latinate bases. It shares its root with related English words such as "extend," "extent," "extension," and "tension," all tracing back to the Latin verb for stretching. Cognate formations appear in Romance languages descended from Latin.
How coextensive is actually used
Formal register, common in legal, philosophical, academic, and technical writing. Almost always followed by the preposition "with" to name the thing it shares extent with. Rare in everyday conversation.
Easily confused with coextensive
"Extensive" means large in amount or scope, while "coextensive" means having exactly the same extent or boundaries as something else.
"Coterminous" is a near-synonym referring specifically to shared boundaries, while "coextensive" can also apply to abstract scopes such as rights, powers, or meanings.