Grammaticalization is a universal process of linguistic variation. It occurs in all languages at all times. However, it is a gradual process and it may affect a linguistic unit simultaneously with other processes of language change. Also, since grammar is not clearly delimited against neighboring domains such as discourse principles and the lexicon, ‘grammaticalization’ is a prototypical concept so that there are crystal-clear cases of grammaticalization and processes of linguistic change that only marginally fall under grammaticalization.
Introductory examples come from the history of English. A rather straightforward example is the creation of the English immediate future of the structure [be going to [X]V ]V. At its origin, this was a specific type of a motion-cum-purpose construction, viz. a syntactic construction composed of the progressive form of the basic motion verb go and an infinitival specifying the goal of the movement. Given these semantics, X is necessarily in the immediate future. Grammaticalization converts this syntactic construction into a periphrastic verb form. It desemanticizes the original construction by eliminating the motion component and the purpose component, leaving only the immediate future component. As a consequence, use of this periphrasis expands; it is no longer confined to purposeful behavior, but may even be used in passive construction like the problem is going to be solved. Also the expression side of the construction is reduced, as going to usually appears as gonna. At this point, the immediate future becomes a member of the tense and aspect paradigm of the language.
Further examples illustrate the grammaticalization of a demonstrative pronoun to a definite article, of the numeral ‘one’ to an indefinite article and of a locating construction to a progressive aspect. All of these developments are well-known from many other languages.
Examples that have been treated in the relevant literature so many times that they do not need repeating here include the abolishment of the Latin case system and its replacement by prepositions which were grammaticalized, in the Romance languages, to case relators indicating syntactic functions. Another such example is the grammaticalization of Latin demonstrative pronouns to personal clitics in the Romance languages.