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Bōsōzoku (暴走族, "violent running tribe") is a Japanese subculture associated with motorcycle clubs and gangs. They were first seen in the 1950s as the Japanese automobile industry expanded rapidly. The first bōsōzoku were known as kaminari-zoku (雷族 "Lightning Tribes"). The word bōsōzoku is also applied to motorcycle gangs, who share an interest in modifications (often illegal) for motorcycles, such as removing the mufflers so that more noise is produced...

A concept (abstract term: conception) is a cognitive unit of meaning—an abstract idea or a mental symbol sometimes defined as a "unit of knowledge," built from other units which act as a concept's characteristics. A concept is typically associated with a corresponding representation in a language or symbology such as a single meaning of a term. There are prevailing theories in contemporary philosophy which attempt to explain the nature of concepts...