A feud, also known in more extreme cases as a blood feud, vendetta, faida, clan war, gang war, private war, or mob war, is a long-running argument or fight, often between social groups of people, especially families or clans. Feuds begin because one party perceives itself to have been attacked, insulted, injured, or otherwise wronged by another. Intense feelings of resentment trigger an initial retribution, which causes the other party to feel greatly aggrieved and vengeful. The dispute is subsequently fueled by a long-running cycle of retaliatory violence. This continual cycle of provocation and retaliation means that feuds can persist for generations and may result in extreme acts of violence. They can be interpreted as an extreme outgrowth of social relations based in family honor, marriage, or competition over property.