아래 토끼님의 글을 보고 위키피디아에서 마피아와 갱의 관계가 어떻게 되는지 한번 찾아 봤어요. 토끼님이 댓글에서 얘기하신대로 갱이 마피아보다 더 넓은 개념이라는 것이 맞는 것 같아요. 그러니까 갱은 일반적으로 범죄집단을 통칭하는 용어로 제시 제임스나 알 카포네와 같은 소규모 조직도 있고 마피아나 삼합회 같은 거대 조직도 있다는 얘기네요.

그리고 우리나라에서 부르는 깡패라는 호칭은 영어 Gang과 패거리를 일컫는 패를 조합해서 만들었다는 설도 있더라고요.

In modern usage, the term "gang" is generally used for a criminal organization, and the term "gangster" invariably describes a criminal. Much has been written on the subject of gangs, although there is no clear consensus about what constitutes a gang or what situations lead to gang formation and evolution. There is agreement that the members of a gang have a sense of common identity and belonging, and this is typically reinforced through shared activities and through visual identifications such as special clothing, tattoos or rings. Some preconceptions may be false. For example, the common view that illegal drug distribution in the United States is largely controlled by gangs has been questioned.

A gang may be a relatively small group of people who cooperate in criminal acts, as with the Jesse James gang, which ended with the leader's death in 1882. But a gang may be a larger group with a formal organization that survives the death of its leader. The Chicago Outfit created by Al Capone outlasted its founders imprisonment and death, and survived into the 21st century. Large and well structured gangs such as the Mafia, Triads or even outlaw motorcycle gangs can undertake complex transactions that would be far beyond the capability of one individual, and can provide services such as dispute arbitration and contract enforcement that parallel those of a legitimate government.

United States and Canada

As American society and culture developed, new immigrants were relocating to the United States. The first major gangs in 19th century New York City were the Irish gangs such as the Whyos and the Dead Rabbits. These were followed by the Italian Five Points Gang and later a Jewish gang known as the Eastman Gang. There were also "nativist" anti-immigration gangs such as the Bowery Boys. The American Mafia arose from offshoots of the Mafia that emerged in the United States during the late nineteenth century, following waves of emigration from Sicily. There were similar offshoots in Canada among Italian Canadians.

In the later 1800s many Chinese emigrated to the United States, escaping from insecurity and economic hardship at home, at first working on the west coast and later moving east. The new immigrants formed Chinese Benevolent Associations. In some cases these evolved into Tongs, or criminal organizations primarily involved in gambling. Members of Triads who migrated to the United States often joined these tongs. With a new wave of migration in the 1960s, street gangs began to flourish in major cities. The tongs recruited these gangs to protect their extortion, gambling and narcotics operations