A gang is a group of good friends or family with identifiable leadership and internal organization, identifying with or claiming control over territory in a community, and engaging either individually or collectively in illegal or violent behavior. Some criminal gang members are "jumped in" or have to prove their loyalty by committing acts such as theft or violence. A member of a gang may be called a gangster or a thug.
The word "gang" derives from the past participle of Old English gan, meaning "to go". It is cognate with Old Norse gangster, meaning "journey." It typically means a group of people, and may have neutral, positive or negative connotations depending on usage.
In discussing banditry in American history Barrington Moore, Jr. suggests that gangsterism as a "form of self-help which victimizes others" may appear in societies which lack strong "forces of law and order"; he characterizes European feudalism as "mainly gangsterism that had become society itself and acquired respectability".
A wide variety of gangs, such as the Order of Assassins, the Damned Crew, Adam the Leper's gang, Penny Mobs, Indian Thugs, Chinese Triads, Snakehead, Japanese Yakuza, Irish mob, Pancho Villa's Villistas, Dead Rabbits, American Old West outlaw gangs, Bowery Boys, Chasers, the Italian mafia, Jewish mafia, and Russian Mafia crime families have existed for centuries. According to some estimates the Thuggee gangs in India murdered 1 million people between 1740 and 1840.