ABSTRACT
This chapter sets out a range of theoretical issues and empirical questions that arise when the concept of compositionality and the fact of language change are juxtaposed. In its modern form the principle of compositionality is attributed to the German mathematician and philosopher Gottlob Frege, and thus is contemporary with the great nineteenth-century explosion of historical linguistics. Despite the considerable quantity of research into compositionality over the years, very little of that debate acknowledges the fact that languages change, including in ways that threaten the working of natural languages as compositional systems. Grammaticalisation by contrast leads to innovative structures, which can introduce new forms of compositionality, as we saw with the emergence of the Romance periphrastic perfects, and in the long run lead to some degree of noncompositionality. A phenomenon that runs directly counter to both compositionality and analysability is defectiveness, that is to say the circumstance in which the expected form simply is not present in the language.
