Lexicon

A lexicon is the vocabulary of a person, language, or branch of knowledge (such as nautical or medical). 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 ); 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.

Items in the lexicon are called lexemes, or lexical items, 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.

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