“Language shift” is used to describe the event of a community abandoning their language for another. It is also called “language assimilation” or “language transfer”. It is a social change and is spurred on by the change in aspirations of a society. A language shift isn’t a structural change.
The change, in fact, happens as a result of coming into contact with another language. Language shift denotes the extinction of the old language and the propagation of the new language. Sometimes, language shift occurs because of a conscious choice, and at other times, it is unplanned.
Language shift is studied under sociolinguistics, and no causal theory has yet been determined. Language shift may or may not result in language death and could possibly be reversed if the degree to which a language is disrupted is recognized. The disrupted language can then be helped towards revitalization by concentrated efforts.
It has been observed that languages which are considered to be higher in status are often discarded for languages which are perceived to be inferior by their native speakers. Latin America shows an example of language shift where English is being spoken over Latin more and more. Such examples can be found all over the world.