Decorum is both criterion and principle of successful and cooperative communication within the scope of a persuasive communication model. It operates as a criterion due to its ability to ensure a suitable linguistic code and it operates as a principle due to its function as an ethical norm. Both in conjunction are prerequisites for a successful speech. The decorum is not understood as a predefined norm for every rhetorical situation, instead it has to be redefined each time. Thus, it necessarily has a relational quality which results from the situation itself and from the judgement of the recipient.
Decorum is understood as part of rhetoric in the sense of a civilian ethos which demarcates rhetoric against manipulation and propaganda.