What is "zoku"

is a Sino-Japanese term meaning tribe, clan, or family. As a suffix it has been used extensively within Japan to define subcultural phenomena, though many zoku do not acquire the suffix (e.g. cosplay).

A zoku may be labeled with a Japanese stem (e.g. kaminari zoku) or a foreign language ( gairaigo) stem (e.g. saike zoku, where saike comes from "psychedelic").

As with the usual practice elsewhere, subcultures in Japan have almost certainly been labeled by an outsider to the group, often an influential person in the media.