To extend to the same distance, degree, or space as something else; to reach the same boundaries.
From 'co-' (together) plus 'extend,' which comes from Latin 'extendere' (to stretch out). This term is used in geometry, logic, and philosophy to describe things with identical scope or boundaries.
In logic, 'bachelor' and 'unmarried man' coextend—they reach exactly the same boundaries and refer to the identical group of people, which is why philosophers consider them logically equivalent.
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