A neologism 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 accepted into mainstream language. Neologisms are often directly attributable to a specific person, publication, period, or event. Neolexia ("new word", or the act of creating a new word) is a synonym.
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. A neologism may also be a new usage of an existing word, sometimes called a semantic extension. This is distinct from a person's idiolect, one's unique patterns of vocabulary, grammar, and pronunciation.