A lexicon (plural: lexicons, rarely lexica) is the

vocabulary A vocabulary (also known as a lexicon) is a set of words, typically the set in a language or the set known to an individual. The word ''vocabulary'' originated from the Latin , meaning "a word, name". It forms an essential component of languag ...

of a

language Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed language, signed forms, and may also be conveyed through writing syste ...

or branch of

knowledge Knowledge is an Declarative knowledge, awareness of facts, a Knowledge by acquaintance, familiarity with individuals and situations, or a Procedural knowledge, practical skill. Knowledge of facts, also called propositional knowledge, is oft ...

(such as

nautical Seamanship is the art, competence, and knowledge 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 topic ...

medical Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

). In

linguistics Linguistics is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), Morphology (linguistics), morphology (structure of words), phonetics (speech sounds ...

, 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 ta ...

s. The word ''lexicon'' derives from

Greek Greek may refer to: 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 of all kno ...

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, grammar is the set of rules for how a natural language is structured, as demonstrated by its speakers or writers. Grammar rules may concern the use of clauses, phrases, and words. The term may also refer to the study of such rul ...

, 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, while a free morpheme (or unbound morpheme) is one that can stand alone. A bound morpheme is a type of bound f ...

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. The main two categories are Morphological derivation, derivational and inflectional affixes. Derivational affixes, such as ''un-'', ''-ation' ...

es). In some analyses,

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

s and certain classes of

idiom An idiom is a phrase or expression that largely or exclusively carries a Literal and figurative language, figurative or non-literal meaning (linguistic), meaning, rather than making any literal sense. Categorized as formulaic speech, formulaic ...

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 t ...

s and other

phraseme A phraseme, also called a set phrase, fixed expression, multiword expression (in computational linguistics), or idiom, is a multi-word or multi-morphemic utterance whose components include at least one that is selectionally constrained or restri ...

s 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 Alphabetical order, alphabetically (or by Semitic root, consonantal root for Semitic languages or radical-and-stroke sorting, radical an ...

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 is a group of lexemes generated by

inflectional morphology In linguistic morphology, inflection (less commonly, inflexion) is a process of word formation in which a word is modified to express different grammatical categories such as tense, case, voice, aspect, person, number, gender, mood, ...

. Lemmas are represented in dictionaries by headwords that list the

citation form In morphology and lexicography, a lemma (: 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'' are forms of the ...

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, such as

determiners Determiner, also called determinative (abbreviated ), is a term used in some models of grammatical description to describe a word or affix belonging to a class of noun modifiers. A determiner combines with a noun to express its reference. Exampl ...

pronoun In linguistics and grammar, a pronoun (Interlinear gloss, glossed ) is a word or a group of words that one may substitute for a noun or noun phrase. Pronouns have traditionally been regarded as one of the part of speech, parts of speech, but so ...

s, 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

noun In grammar, a noun is a word that represents a concrete or abstract thing, like living creatures, places, actions, qualities, states of existence, and ideas. A noun may serve as an Object (grammar), object or Subject (grammar), subject within a p ...

s and

verb A verb is a word that generally conveys an action (''bring'', ''read'', ''walk'', ''run'', ''learn''), an occurrence (''happen'', ''become''), or a state of being (''be'', ''exist'', ''stand''). In the usual description of English, the basic f ...

s, have highly active generation mechanisms and their lexemes are more

semantic Semantics is the study of linguistic Meaning (philosophy), meaning. It examines what meaning is, how words get their meaning, and how the meaning of a complex expression depends on its parts. Part of this process involves the distinction betwee ...

in nature.

Lexicalization and other mechanisms in the lexicon

A central role of the lexicon is documenting established ''lexical norms and conventions''.

Lexicalization In linguistics, lexicalization is the process of adding words, set phrases, or word patterns to a language's lexicon. Whether '' word formation'' and ''lexicalization'' refer to the same process is controversial within the field of linguistics. M ...

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 Linguistics Linguistics terminology Vocabulary