In this volume, long-standing assumptions about the formal changes involved in grammaticalization are evaluated in the light of the striking diversity of human languages. To this end, the traditional notions of morphological coalescence, syntactic fixation and phonological erosion are reassessed with regard to their relationship with the diachronic changes affecting the function of the construction and with larger-scale typological changes that affect the language as a whole (especially, shifts in morphological type and word-order patterns). The author reaches the conclusion that suprasegmental phonological erosion and syntactic fixation (redefined in a template-based framework) are direct consequences of functional change and are therefore significant indicators of grammaticalization, whereas coalescence and segmental erosion are independently motivated by psycholinguistic, rather than strictly grammatical factors.