Extensionalne

Extensionalne refers to a concept in logic and semantics related to the meaning of terms or expressions. An extensional definition of a term or expression focuses on the set of all actual things or instances that the term refers to. In contrast, an intensional definition focuses on the properties or criteria that define membership in that set. For example, the extension of the term "dog" is the set of all individual dogs that exist or have existed. The intension of "dog" might be something like "a domesticated canine mammal, typically with a long snout, an acute sense of smell, and a barking, howling, or whining voice."

The distinction between extension and intension is important in understanding how meaning works. Two terms can have the same intension but different extensions, or vice versa. For instance, "the morning star" and "the evening star" have different extensions in that they refer to different celestial phenomena at different times, but their intension might be considered the same if both are defined as "the brightest object in the sky after sunset or before sunrise." In formal logic, extensionality often plays a role in set theory and the interpretation of logical formulas. Extensional equivalence means that two expressions refer to the same set of objects.