Extensional and Intensional

“In logic, extensional and intensional definitions are two key ways in which the objects, concepts, or referents a term refers to can be defined. They give meaning or denotation to a term.

An intensional definition gives meaning to a term by specifying necessary and sufficient conditions for when the term should be used. In the case of nouns, this is equivalent to specifying the properties that an object needs to have in order to be counted as a referent of the term.

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An extensional definition gives meaning to a term by specifying its extension, that is, every object that falls under the definition of the term in question.”

I believe Eco contends in Semiotics and the Philosophy of Language that the distinction between intensional and extensional definitions is a false one.