The article discusses definitions of grammaticalization, pragmaticalization and (inter) subjectification in order to clarify the relations between these terms. While grammaticalization is defined as a functionally motivated, complex type of language change, (inter) subjectification is shown to be a specific type of semantic change. Pragmaticalization, finally, is argued to represent a subclass of grammaticalization, which displays essential core features of grammaticalization processes, but is distinguished from other subtypes of grammaticalization processes by specific characteristic traits (concerning function and domain as well as syntactic integration). This is demonstrated by a survey of the diachronic development of several modal particles in German (among them aber, eben, ruhig). The more general theoretical stance taken here is that the notion of grammar and hence grammaticalization has to be conceived broad enough in order to encompass this type of discourse functions.