Rudeness (also called effrontery) is a display of disrespect by not complying with the social norms or etiquette of a group or culture. These norms have been established as the essential boundaries of normally accepted behaviour. To be unable or unwilling to align one's behaviour with these norms known to the general population of what is socially acceptable is to be rude and are enforced as though they were a sort of social law, with social repercussions or rewards for violators or advocates.
Rudeness "constituted by deviation from whatever counts as politic in a given social context, is inherently confrontational and disruptive to social equilibrium" (Kasper, 1990, p. 208). Rudeness, particularly with respect to speech, is necessarily confrontational at its core.
Forms of rudeness include acting inconsiderate, insensitive, deliberately offensive, impolite, a faux pas, obscenity, profanity and violating taboos such as deviancy. In some cases, an act of rudeness can go so far as to be a crime, for example, the crime of hate speech.
Both manners and morality deal with whether a thing is morally good or bad, but at different levels. Unlike morality, which, for example, condemns murder as a violation of a person, manners primarily concerns itself with violations of human dignity, rather than the person's health or property (Martin, 1996, p. 123). Rude behaviour is a violation of human dignity or of the respect due to others.
The specific actions that are considered polite or rude vary dramatically by place, time, and context. Differences in social role, gender, social class, religion, and cultural identity may all affect the appropriateness of a given behaviour. Consequently, a behaviour that is considered perfectly acceptable by one group of people may be considered clearly rude by another. For example, in medieval and Renaissance Europe, it was rude to indicate that a man wearing a mask in public could be recognized (Palleschi 2005). Instead, polite behaviour demanded that the masked person be treated as a completely unknown person and that no one ever attribute the masked person's actions to the individual who performed them. By contrast, in the modern era, greeting a friend by name while he is wearing a mask, or talking to him later about his costume or activities, is not generally regarded as rude.