This special issue of the Nordic Journal of Linguistics is devoted to grammaticalization. In our call for papers, we emphasized that the term should be understood in a broad sense, inviting empirically as well as theoretically based papers. Almost all aspects of language may be studied from a grammaticalization perspective, and the concept is generally also understood as including diachronic as well as synchronic linguistic studies. The three selected papers reflect some of the richness of the field of grammaticalization.