The way speakers in multilingual contexts develop own varieties in their interactions sheds light on code switching and multimodal dynamic co-constructions of grammar in use. This volume explores the intersection of multimodality and language use of multilingual speakers. Firstly, theoretical frames are discussed and empirical studies involving Catalan, German and Spanish as L1, L2 or FL are presented interconnecting verbal and gestural modalities into grammar description or exploring actions as sources for gestures, which may nonverbally represent the argument in German dynamic motion verbs. Other chapters focus on positionings in interviews, lexical access searches or proxemics in greetings and farewells. The contributions secondly focus on verbal features of language use in multilingual contexts related to self-representation and co-construction of identity through code-switching, deixis or argumentative reasoning in different communicative events based on multilingual data of languages including Croatian, English, Italian, Brazilian-Portuguese and Polish. The findings call for a reviewed conception of grammar description with implications also for the conceptualization of deixis, for L2/foreign language acquisition and language teaching policies.