In sociology, deviance describes an action or behavior that violates social norms, including formally enacted rules (e.g., crime), as well as informal violations of social norms (e.g., rejecting folkways and mores). It is the purview of sociologists, psychologists, psychiatrists, and criminologists to study how these norms are created, how they change over time and how they are enforced.Norms are rules and expectations by which members of society are conventionally guided. Deviance is an absence of conformity to these norms. Social norms differ from culture to culture. For example, a deviant act can be committed in one society that breaks a social norm there, but may be normal for another society.Viewing deviance as a violation of social norms, sociologists have characterized it as "any thought, feeling, or action that members of a social group judge to be a violation of their values or rules "or group" conduct, that violates definitions of appropriate and inappropriate conduct shared by the members of a social system. The departure of certain types of behavior from the norms of a particular society at a particular time and "violation of certain types of group norms where behavior is in a disapproved direction and of sufficient degree to exceed the tolerance limit of the community.Deviance can be relative to time and place because what is considered deviant in one social context may be non-deviant in another (e.g., fighting during a hockey game vs. fighting in a nursing home). Killing another human is considered wrong, except when governments permit it during warfare or for self defense. Deviant actions can be mala in se or mala prohibita.