Decorum is essentially the suitable way of presenting something for a given circumstance. The word has definitions for everyday usage and a specific definition relating to the field of rhetoric. In ordinary usage, the word decorum basically means good taste and appropriate propriety in both dress and conduct. Within the field of rhetoric, it is the practice of ensuring that the words used are suitable for the subject matter, the audience being addressed, the occasion, and the person who is speaking the words. Overall, the word means to be presented in a way suitable for the given occasion.
The word decorum has origins in Latin, coming from words like decor and decorus which have to do with beauty or what is pleasing to the senses. In ordinary English, the word is used to mean the appropriate conventions of dress and conduct required in specific situations. For example, anybody who attends the opera is expected to have a particularly high level of decorum.
Most of the time, the usage of the word in modern English is mainly synonymous with manners and being well-presented. The rules of decorum can be thought of as the rules of etiquette, which tend to be different for different situations but are generally intended to show respect to the host and the other guests present in any formal situation. If somebody is unaware of these codes, he or she is said to have “no sense of decorum.”
Ancient Greece’s rhetoricians have also created a specific definition for the term decorum. The meaning is closely related to the modern meaning, but it is specifically related to the field of argumentation and debate. Words used in an argument should be suited to the subject being discussed and the person who is discussing them, as well as being appropriate for the circumstances, occasion, and audience being addressed.
It is generally thought that if rhetorical decorum is achieved the argument will be well received by those present. Rhetorical “vices” are breaches of the necessary decorum for presenting an argument in writing and speech and will result in an unfavorable reception. Many of these vices have been identified in the study of rhetoric. Decorum relies heavily on its appropriateness for a particular context or audience, however, so its evaluation can be rather subjective. What may be seen as a vice in one situation may be wholly appropriate in another.