A neologism (/niːˈɒlədʒɪzəm/; from Greek νέο- néo-, "new" and λόγος lógos, "speech, utterance") is the name for a relatively new or isolated term, word, or phrase that may be in the process of entering common use, but that has not yet been fully accepted into mainstream language. Neologisms are often directly attributable to a specific person, publication, period, or event.
The term neologism is first attested in English in 1772, borrowed from French néologisme (1734). A proponent of a new word or doctrine may be called a neologist. Neologists might study cultural and ethnic vernacular.
The term neologism has a broader meaning that includes not only "an entirely new lexical item" but also an existing word whose meaning has been altered. Sometimes, the latter process is called semantic shifting, or semantic extension. Neologisms are distinct from a person's idiolect, one's unique patterns of vocabulary, grammar, and pronunciation.
Neologisms are usually introduced when an individual or individuals find that a specific notion is lacking a term in a language, or when the existing vocabulary is insufficiently detailed. The law, governmental bodies, and technology have a relatively high frequency of acquiring neologisms.
In psychiatry, the term neologism is used to describe the use of words that have meaning only to the person who uses them, independent of their common meaning. This tendency is considered normal in children, but in adults it can be a symptom of psychopathy or a thought disorder (indicative of a psychotic mental illness, such as schizophrenia). People with autism also may create neologisms.