When I entered her shop, my friend turned to me and said: « Arà, che si dice? » (‘Hey there, how you doing?’). This was not a full-fledged sentence in Italian, as she had thrown a little Sicilian word in – arà . It was a greeting, of course, but also a way of expressing her surprise at seeing me there, and a way of prompting me to start our conversation. The fact she used Sicilian had a clear meaning too: the vernacular indicates a shared social identity. In a nutshell, this book analyses the cases of Sicilian arà and mentri to understand the complexity of discourse markers: what functions they perform, how they evolve historically, and what their social meaning is in a bilingual speech community.