Co-extensive refers to two or more things that have the same extent or range, or that occupy the same space or time. Synonyms for co-extensive include conterminous, coterminous, coincidental, concurrent, coequal, coextensile, commensurate, correspondent, corresponding, and equal. These words express the idea of things being equal in length, size, scope, duration, or significance. They are often used in academic, scientific, or legal contexts to describe relationships between different entities or variables. Whether you use co-extensive or one of its synonyms, the meaning remains the same: that two or more things are united or connected in a way that is inseparable.