Language shift is a social phenomenon, whereby one language replaces another in a given (continuing) society. It is due to underlying changes in the composition and aspirations of the society, which goes from speaking the old to the new language. By definition, it is not a structural change caused by the dynamics of the old language as a system. The new language is adopted as a result of contact with another language community, and so it is usually possible to identify the new language as “the same” as, that is, a descendant of, a language spoken somewhere else, even if the new language has some new, perhaps unprecedented, properties on the lips of the population that is adopting it. Language shift results in the spread of the new language that is adopted, and may result in the endangerment or loss of the old language, some or all of whose speakers are changing their allegiance. As a result, some readings on language spread and endangerment are relevant to language shift. Language shift may be an object of conscious policy; but equally it may be a phenomenon which is unplanned, and often unexplained. Consequently, readings in language policy (especially those on status planning) often relate to it. The conditions of imperial relations between societies, and the special links mediated nowadays by technological inventions, often worldwide and at a particularly rapid pace, are thought by some to require special theories.`