This chapter offers an overview of the diamesic dimension of language variation, traditionally centred on the medium used to produce or deliver the message. Given that languages always vary along several dimensions simultaneously, the first step is to clarify how Italian changes according to the communicative situation, focusing on the role played by the degree of formality and the resulting registers. The second part of the chapter discusses the concepts and parameters allowing us to grasp how languages in general, and Italian in particular, change diamesically, introducing the notion of conceptualization. The last part of the chapter provides a detailed account of the linguistic features of four diamesic realizations of Italian: spoken face-to-face conversation, movie dialogues, neo-standard Italian, and so-called e-italiano.