This book combines theoretical work in linguistic pragmatics and sociolinguistics with empirical work based on a corpus of London adolescent conversation. It makes a general contribution to the study of pragmatic markers, as it proposes an analytical model that involves notions such as subjectivity, interactional and textual capacity, and the distinction between contextual alignment/divergence. These notions are defined according to how information contained in an utterance interacts with the cognitive environment of the hearer. Moreover, the model captures the diachronic development of markers from lexical items via processes of grammaticalisation, arguing that markerhood may be viewed as a gradient phenomenon. The empirical work concerns the use of like as a marker, as well as a characteristic use of two originally interrogative forms, innit and is it, which are used as attitudinal markers throughout the inflectional paradigm, despite the fact that they contain a third person singular neuter pronoun. The author provides an in-depth analysis of these features in terms of pragmatic functions, diachronic development and sociolinguistic variation, thus adding support to the hypothesis that adolescents play an important role in language variation and change.