Neologism is a word that is new (15 to 20 years or less) but older and used more than a protologism. Neologisms are often directly attributable to a specific person, publication, period, or event. Νεολεξία (Greek: a "new word", or the act of creating a new word) is a synonym for it. The term neologism was first used in English in 1772, borrowed from French néologisme (1734).

Using an existing word or phrase in a new context is also called neologism. The process of using a word in such a new context is sometimes called a semantic extension. A new word that has not been used by anyone but the inventer is a protologism.