Formally, in linguistics, a lexicon is a language's inventory of lexemes. The word "lexicon" derives from the Greek λεξικόν (lexicon), neuter of λεξικός (lexikos) meaning "of or for words".
Linguistic theories generally regard human languages as consisting of two parts: a lexicon, essentially a catalogue of a language's words (its wordstock); and a grammar, a system of rules which allow for the combination of those words into meaningful sentences. The lexicon is also thought to include bound morphemes, which cannot stand alone as words (such as most affixes). In some analyses, compound words and certain classes of idiomatic expressions and other collocations are also considered to be part of the lexicon. Dictionaries represent attempts at listing, in alphabetical order, the lexicon of a given language; usually, however, bound morphemes are not included.
Size and OrganizationEdit
Items in the lexicon are called lexemes or word forms. Lexemes are not atomic elements but contain both phonological and morphological components. When describing the lexicon, a reductionist approach is used, trying to remain general while using a minimal description. To describe the size of a lexicon, lexemes are grouped into lemmas. A lemma is a group of lexemes generated by inflectional morphology. Lemmas are represented in dictionaries by headwords which list the citation forms and any irregular forms, since these must be learned to use the words correctly. Lexemes derived from a word by derivational morphology are considered new lemmas. The lexicon is also organized according to open and closed categories. Closed categories, such as determiners or pronouns, are rarely given new lexemes; their function is primarily syntactic. Open categories, such as nouns and verbs, have highly active generation mechanisms and their lexemes are more semantic in nature.
Lexicalization and other mechanisms in the lexiconEdit
A central role of the lexicon is the documenting of established lexical norms and conventions. Lexicalization is the process in which new words, having gained widespread usage, enter the lexicon. Since lexicalization may modify lexemes phonologically and morphologically, it is possible that a single etymological source may be inserted into a single lexicon in two or more forms. These pairs, called a doublet, are often close semantically. Two examples are aptitude versus attitude and employ versus imply. The mechanisms, not mutually exclusive, are: • Innovation, the planned creation of new roots (often on a large-scale), such as slang, branding. • Borrowing of foreign words. • Compounding (composition), the combination of lexemes to make a single word. • Abbreviation of compounds. • Acronyms, the reduction of compounds to their initial letters, such as NASA and laser (from "LASER"). • Inflection, a morphology change with a category, such as number or tense. • Derivation, a morphological change resulting in a change of category. • Agglutination, the compounding of morphemes into a single word. In complex words, constituents may be dropped
The term "lexicon" is generally used in the context of single language. Therefore, multi-lingual speakers are generally thought to have multiple lexicons. Speakers of language variants (Brazilian Portuguese and European Portuguese, for example) may be considered to possess a single lexicon. Thus a cash dispenser (British English) as well as an automatic teller machine or ATM in American English would be understood by both American and British speakers, despite each group using different dialects. When linguists study a lexicon, they consider such things as what constitutes a word; the word/concept relationship; lexical access and lexical access failure; how a word's phonology, syntax, and meaning intersect; the morphology-word relationship; vocabulary structure within a given language; language use (pragmatics); language acquisition; the history and evolution of words (etymology); and the relationships between words, often studied within philosophy of language. Various models of how lexicons are organized and how words are retrieved have been proposed in psycholinguistics, neurolinguistics and computational linguistics.