Behavior in keeping with good taste and propriety. The guests were expected to maintain a level of decorum during the formal dinner.
Etiquette or a set of conventions appropriate to a particular social setting. The decorum of the courtroom demanded that everyone remain silent while the judge was speaking.
The principle of suitability in art or literature, whereby the style or tone matches the subject, genre, or audience. Classical critics insisted on decorum, ensuring that tragic heroes spoke in elevated language.