A neologism can be a brand new word gaining usage in a language, or a new meaning for a word already in existence. Such a term isn't typically in common use, but may become so if it is used often. Neologisms can come from a variety of places and might be gleaned from scientific or technical language, come from other languages, be derived by putting two words together, or they may be solely invented, as in the case of words like "Jabberwocky" from the famous Lewis Carroll poem. Linguistic specialists suggest new words often migrate into a language most with great cultural changes or with the integration of two cultures that speak two different languages. Arguably, things like social media may also have great influence on what new words become part of a language.
Linguists often classify the neologism by its degree of use in a language. The newborn word is at first unstable, and it’s hard to guess whether it will take hold and eventually be a word that most people know and use. A diffused neologism means that many people are using the word, but it doesn’t yet have formal recognition as a word, and ultimately, if the word remains popular it may attain stable status. It has become part of the language and is likely to be defined in dictionaries.
There are some who welcome the neologism as a natural process of language because new words become part of language constantly. Others view neologisms as corruptions of the principal language and they may argue against their inclusion, especially in any type of formal writing venue. This second group usually loses the argument because language is not static; it expands or shrinks at all times, and word use in the general populace or even in academia doesn’t remain the same.
On the other hand, students should be warned that use of a diffused or unstable neologism in academic writing is not likely to be met with favor. If a writing assignment requires formal language, it’s usually not appropriate to use a newly coined word. Ironically, many neologisms come from academia, either from the highly technical language of science or from literature.
There is another definition of neologism that is used in psychiatric medicine. Words that are made up by those with severe mental illness or autism, and are used and repeated by the people who make them up, may also be called neologisms. In this case, the words have personal meaning only and don’t spread to the general language. This behavior is, by no means, only characteristic of the mentally ill. When children learn language, they frequently make up words too. Twins may develop a unique vocabulary that can only be understand by each other, but in most cases this language will not spread elsewhere.