The mental lexicon is defined as a mental dictionary that contains information regarding the word store of a language user, such as their meanings, pronunciations, and syntactic characteristics.[1] The mental lexicon is used in linguistics and psycholinguistics to refer to individual speakers' lexical, or word, representations. However, there is some disagreement as to the utility of the mental lexicon as a scientific construct.[2]

The mental lexicon differs from the lexicon more generally in that it is not just a collection of words; instead, it deals with how those words are activated, stored, processed, and retrieved by each speaker/hearer. Furthermore, entries in the mental lexicon are interconnected with each other on various levels. An individual's mental lexicon changes and grows as new words are learned and is always developing, but there are several competing theories seeking to explain exactly how this occurs. Some theories about the mental lexicon include the spectrum theory, the dual-coding theory, Chomsky's nativist theory, as well as the semantic network theory. Neurologists and neurolinguists also study the areas of the brain involved in lexical representations. The following article addresses some of the physiological, social, and linguistic aspects of the mental lexicon.