A lexicon is the

vocabulary A vocabulary is a set of familiar words within a person's language. A vocabulary, usually developed with age, serves as a useful and fundamental tool for communication and acquiring knowledge. Acquiring an extensive vocabulary is one of the la ...

of a

language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...

or branch of

knowledge Knowledge can be defined as awareness of facts or as practical skills, and may also refer to familiarity with objects or situations. Knowledge of facts, also called propositional knowledge, is often defined as true belief that is distinc ...

(such as

nautical Seamanship is the art, knowledge and competence of operating a ship, boat or other craft on water. The'' Oxford Dictionary'' states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea." It involves topics a ...

medical Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...

). In

linguistics Linguistics is the scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, particularly its nature and structure. Linguis ...

, a lexicon is a language's inventory of

lexeme A lexeme () is a unit of lexical meaning that underlies a set of words that are related through inflection. It is a basic abstract unit of meaning, a unit of morphological analysis in linguistics that roughly corresponds to a set of forms taken ...

s. The word ''lexicon'' derives from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word (), neuter of () 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 In linguistics, the grammar of a natural language is its set of structure, structural constraints on speakers' or writers' composition of clause (linguistics), clauses, phrases, and words. The term can also refer to the study of such constraint ...

, a system of rules which allow for the combination of those words into meaningful sentences. The lexicon is also thought to include

bound morpheme In linguistics, a bound morpheme is a morpheme (the elementary unit of morphosyntax) that can appear only as part of a larger expression; a free morpheme (or unbound morpheme) is one that can stand alone. A bound morpheme is a type of bound form, ...

s, which cannot stand alone as words (such as most

affix In linguistics, an affix is a morpheme that is attached to a word stem to form a new word or word form. Affixes may be derivational, like English ''-ness'' and ''pre-'', or inflectional, like English plural ''-s'' and past tense ''-ed''. They ar ...

es). In some analyses,

compound word In linguistics, a compound is a lexeme (less precisely, a word or sign) that consists of more than one stem. Compounding, composition or nominal composition is the process of word formation that creates compound lexemes. Compounding occurs when ...

s and certain classes of

idiom An idiom is a phrase or expression that typically presents a figurative, non-literal meaning attached to the phrase; but some phrases become figurative idioms while retaining the literal meaning of the phrase. Categorized as formulaic language, ...

atic expressions,

collocation In corpus linguistics, a collocation is a series of words or terms that co-occur more often than would be expected by chance. In phraseology, a collocation is a type of compositional phraseme, meaning that it can be understood from the words th ...

s and other phrases are also considered to be part of the lexicon.

Dictionaries A dictionary is a listing of lexemes from the lexicon of one or more specific languages, often arranged alphabetically (or by radical and stroke for ideographic languages), which may include information on definitions, usage, etymologies, p ...

are lists of the lexicon, in alphabetical order, of a given language; usually, however, bound morphemes are not included.

Size and organization

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,

s are grouped into lemmas. A

lemma Lemma may refer to: Language and linguistics * Lemma (morphology), the canonical, dictionary or citation form of a word * Lemma (psycholinguistics), a mental abstraction of a word about to be uttered Science and mathematics * Lemma (botany), a ...

is a group of lexemes generated by inflectional morphology. Lemmas are represented in dictionaries by headwords that list the

citation form In morphology and lexicography, a lemma (plural ''lemmas'' or ''lemmata'') is the canonical form, dictionary form, or citation form of a set of word forms. In English, for example, ''break'', ''breaks'', ''broke'', ''broken'' and ''breaking'' a ...

s 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 Closed may refer to: Mathematics * Closure (mathematics), a set, along with operations, for which applying those operations on members always results in a member of the set * Closed set, a set which contains all its limit points * Closed interval, ...

, such as

determiners A determiner, also called determinative (abbreviated ), is a word, phrase, or affix that occurs together with a noun or noun phrase and generally serves to express the reference of that noun or noun phrase in the context. That is, a determiner m ...

or pronouns, are rarely given new lexemes; their function is primarily

syntactic In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure (constituency), ...

. Open categories, such as nouns and verbs, have highly active generation mechanisms and their lexemes are more

semantic Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and comput ...

in nature.

Lexicalization and other mechanisms in the lexicon

A central role of the lexicon is the documenting of established ''lexical norms and conventions''. Lexicalization is the process by 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 Doublet is a word derived from the Latin ''duplus'', "twofold, twice as much", {{Authority control Lexis (linguistics), Linguistics Linguistics terminology Vocabulary