Abstract: The paper discussed the concept of mental lexicon or mental dictionary and some other studies related to the area of mental lexicon. How lexical items are accessed, acquired and ordered in the mind is a controversial area for both linguists and psychologists. The mental lexicon is a complicated structure organized in many ways. This paper discusses the notion of mental lexicon and what are the similarities and contrasts between mental lexicon and physical dictionary, methods and ways used for inquiry and the role of mental lexicon in case of learning and acquisition of language as well as an overview on the language and memory. The paper covers research findings in this area.