Coextensive

The city and county of San Francisco are coextensive.

And then there are the catch-all provisions: rules that allow police to stop drivers for conduct that complies with all the rules on the books, but that officers consider "imprudent" or "unreasonable" under the circumstances, or that describe the offense in language so broad as to make a vioation virtually coextensive with the officer's unreviewable personal judgment.

His life is almost co-extensive with one of the most disastrous periods in Roman history.

Coextensive expressions with different intensions cannot in general be substituted for one another within an expression e while preserving the extension of e (assuming that the extension of a declarative sentence is its truth value).