Full Idea
The three main theories of concepts under consideration are the exemplar, the prototype and the knowledge approaches.
Clarification
The knowledge approach is also referred to as the 'theory theory'
Gist of Idea
The main theories of concepts are exemplar, prototype and knowledge
Source
Gregory L. Murphy (The Big Book of Concepts [2004], Ch.13)
Book Reference
Murphy,Gregory L.: 'The Big Book of Concepts' [MIT 2004], p.483