A lexicon (plural: lexicons, rarely lexica) is the vocabulary of a 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 Greek word λεξικόν (lexikon), neuter of λεξικός (lexikos) meaning 'of or for words'.[1]
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).[2] In some analyses, compound words and certain classes of idiomatic expressions, collocations and other phrases are also considered to be part of the lexicon. Dictionaries are lists of the lexicon, in alphabetical order, of a given language; usually, however, bound morphemes are not included.
Items in the lexicon are called lexemes, 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 that 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.
A central role of the lexicon is documenting established lexical norms and conventions. Lexicalization is the process by which new words, having gained widespread usage, enter the lexicon. Since lexicalization[3] 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.[4]
Neologisms are new lexeme candidates which, if they gain wide usage over time, become part of a language's lexicon. Neologisms are often introduced by children who produce erroneous forms by mistake.[7] Other common sources are slang and advertising.
There are two types of borrowings (neologisms based on external sources) that retain the sound of the source language material: