In linguistics, a lexicon contains the vocabulary and expressions understood by the speaker of a language. The term can also refer to the jargon of a particular profession or activity, such as business language. Grammar and phonetics are not included in the definition. A lexicon is also a synonym for a thesaurus, a reference containing groupings of words that have similar meanings.
Words are the parts of speech that people use to communicate their thoughts. As each person learns the language of his culture, words and their meanings and usage are stored in the mental lexicon. Psycholinguists and neurolinguists study how the words are retrieved from the storehouse within the brain and how they are learned.
The English language contains roughly 600,000 words. Most people only use around 2,000 in their daily speech. Many of the words have more than one definition and various sets of forms, called lexemes. Spanish and French are languages in which conjugation creates new forms of its verbs with respect to gender, number or person, and idiomatic expressions. A collection containing all the lexemes in a language is referred to as a full-form lexicon.
A specialized lexicon that relates to a profession contains only the terms used specifically in that profession. Examples of business language include financial words, those relating to personnel issues, and others comprising corporate jargon. The medical profession has its own vocabulary with abbreviations and acronyms health care workers use to communicate among themselves. Sports, technical professions, and the arts also employ specific terms unique to them.
Slang is a miniature lexicon specialized to a particular region or group. Adolescents typically have their own words for things, and they change drastically with each generation. Long-time fans of a television show or film may create their own dictionary of terms and expressions from the show. Slang may not have meaning to anyone outside the group. With the Internet, slang can spread exponentially and updates are instantaneous, providing linguists with current data they can use to study the vernacular.
Writers use a thesaurus to search for words to convey an idea. Choosing the wrong word can alter the way a sentence expresses that concept. The collected lexicon offers them many choices to express the exact meaning they intend. Since language is dynamic, an updated thesaurus will include new words as they are coined.