During the Post-classical period (III BC – VI AD), Greek underwent fundamental changes in all linguistic domains (phonology/semantics/morphology/syntax): for example, vowel length distinction was lost, vocabulary was extended through derivation and borrowing, inflectional morphology was restructured, and the optative mood disappeared. Many of these changes have been studied in the light of language contact, that is, contacts between Greek on the one hand and Latin, Hebrew, Aramaic, and Coptic on the other. This research project aims to draw renewed attention to the ‘language-internal ecology’ of Post-classical Greek, studying the impact of linguistic changes in one domain on changes in the same or other domains. To be more specific, the project has three objectives: (i) to analyse to what extent certain morphosyntactic changes can be considered correlated, (ii) to uncover the underlying motivations for such correlations, and (iii) to determine more precisely the diachrony of the linguistic changes under investigation. To realise these objectives, I will make use of the Systemic Functional framework, which offers a holistic and ecological theory of language. My analysis will be based on a corpus of around 5000 documentary texts (letters, petitions, and contracts) from the third century BC until the sixth century AD. Since these texts span a broad time period, often can be dated, and are contextually diverse, they are ideally suited for this type of research.