Abstract of the lecture: In this talk I will examine how language is conceptualised against dialect and examine the role of literary idioms in creating localised and transregional vernaculars. After discussing the ideas of language area, patois, literary idiom, diglossia, multilingualism, language build-up, koeneisation and vernacularisation, the talk will examine the vernacular scene in second-millennium north India, a territory stretching from modern-day Gujarat to Bengal. We can distinguish two models of vernacularisation roughly covering the regions with which Shauraseni and Magadhi Prakrit and Apabhramsha are associated with. While the influential research by Sheldon Pollock proposed a single model of vernacularisation originating from royal courts and then diffusing into wider regions, I will present the importance of mercantile and other networks in creating and maintaining transregional vernaculars, including the early forms of Hindi and Gujarati.