Subtitles are a mixture of speech and writing in the sense that they represent oral utterances in discrete written captions with the transitoriness of speech. The transformation of dialogue into subtitles is influenced by three main factors: captions must integrate with the existing material and semiotic structure of a film; speech has to be presented in an altered written mode and subtitles must be designed so as to take account of viewers' reading capacities (c.f. chapter three).