1. In a manner relating to or determined by the extension or range of application of a term; by reference to the actual objects or instances that fall under a concept rather than by its meaning or definition.
Usage: formal; logic and philosophy

Examples

• Two concepts may be equivalent extensionally even if they differ in meaning.
• The terms 'triangle' and 'three-sided polygon' are extensionally identical because they refer to the same set of objects.
• In logic, extensionally equivalent predicates pick out the same members of a domain.
• We can define a set extensionally by listing all its members.
• The philosopher argued that the two definitions are extensionally the same despite their different formulations.