Cognitive synonymy is a type of synonymy in which synonyms are so similar in meaning that they cannot be differentiated either denotatively or connotatively, that is, not even by mental associations, connotations, emotive responses, and poetic value. It is a stricter (more precise) technical definition of synonymy, specifically for theoretical (e.g., linguistic and philosophical) purposes. In usage employing this definition, synonyms with greater differences (and thus less interchangeability) are often called near-synonyms rather than synonyms.