The first part of this chapter brings together some ideas about the role of words and concepts that are widely agreed in theories of language and cognition, and suggests it would be reasonable to expect these ideas to be applied to the words and concepts used within those theories. The second part argues that this is not always the case. Theorists sometimes use words and concepts in a way that is at odds with their own theories about language and cognition. An explanation for this is offered, and a method for detecting and correcting problems that arise from it is proposed. The focus is phonology, and its application in human (as opposed to computational) domains, such as pronunciation teaching.