Grammaticalization
In historical linguistics and language change, grammaticalization (also known as grammatization or grammaticization) is a process of language change by which words representing objects and actions (i.e. nouns and verbs) transform to become grammatical markers (affixes, prepositions, etc.). Grammaticalization is a powerful aspect of language, as it creates new function words by a process other than deriving them from existing bound, inflectional constructions (i.e., by instead deriving them from content words). An example is the historical evolution of Old English willan ('to want', 'to wish') to the Modern English auxiliary verb will, which can express intention or simply futurity.