A theory of human categorization that was posited by Eleanor Rosch in order to account for experimental findings that she and her colleagues uncovered during the 1970s. Prototype theory holds that there are two basic principles that guide the formation of categories in the human mind: (1) the principle of cognitive economy; and (2) the principle of perceived world structure. These principles together give rise to the human categorization system.

The first principle, the principle of cognitive economy, states that an organism like a human being attempts to gain as much information as possible about its environment while minimizing cognitive effort and resources. This cost-benefit balance drives category formation. In other words, rather than storing separate information about every individual stimulus experienced, humans can group similar stimuli into categories, which maintains economy in cognitive representation. The consequence of this is that humans privilege categories formed at a certain level of informational inclusiveness or complexity.

This level of categorization is known as the basic level of categorization.

The second principle, the principle of perceived world structure, posits that the world around us has correlational structure. For instance, it is a fact about the world that wings most frequently co-occur with feathers and the ability to fly (as in birds) rather than with fur or the ability to breathe underwater. This principle states that humans rely upon correlational structure of this kind in order to form and organize categories. This correlational structure gives rise to a prototype. Since the 1970s Rosch's findings and claims have been called into question. Today, prototype theory is no longer seen as an accurate view of categorization.

Nevertheless, it was historically important for the development of cognitive semantics