ABSTRACT
Most gestures are hand movements but gaze, head movements and facial expressions also play a role in discourse delivery and conversation. Kendon defined gestures as visible action as utterance employed to express ideas in conjunction with spoken words. Depending on the context, the same action, head scratching for instance, can be seen as a comfort movement or as a sign of perplexity or annoyance. This chapter indicates what the study of gestures is about and to describe the variety of gestures that will be considered in the next chapters. In their empirical research, scientists distinguish different kinds of gestures, with different terms, and it is useful to discover the genealogy of the main classification of gestures, to show branching and relationships in the domain. Among co-verbal gestures, some of them are meaningful and relate to an external referent either by demonstratives or by iconic depictions, while others are meaningless and relate to discourse processing or prosody.
