What can be said?

We employ a cluster approach to explore the comparative semantic maps of several markers of modal possibility – the “potential” prefix nga‑ and expressions meaning, roughly, ‘know how to’ and ‘be able to’ – in four South African Nguni languages: isiNdebele, isiZulu, isiXhosa, Siswati. We also compare the Nguni results with results from Xitsonga, a closely related language outside of the Nguni clade. The languages exhibit cross-linguistic differences in the expansion of core meanings, some of which do not appear to follow the cross-linguistically common diachronic pattern in which goal-oriented modality precedes deontic modality. In addition, the distinction between inherent and learned ability is salient in several of these languages. Semantic maps of the markers’ functional distributions further show the diversity of modal systems that can be found even in closely related languages in significant contact with one another.