Otaku is a Japanese word for a person with an obsessive interest, in any field. In Japan it carries a strong negative charge, suggesting devotion at the expense of a social life. Borrowed into English, it softened into a largely neutral or proud label for a devoted anime and manga fan.
Otaku started as an ordinary, formal word for "you" or "your household," and fans of early anime adopted it as an awkwardly polite way to address each other, which is how it stuck to the subculture. In 1980s Japan the word turned sharply negative in the press, coming to mean someone whose obsession with a hobby had consumed their social life, and in Japanese it still carries that sting: it applies to any obsession, train otaku and idol otaku included, and is not a compliment at home.
English borrowed the word in the 1990s and bleached it. Overseas, an otaku is roughly a devoted anime and manga fan, connoting deep knowledge more than dysfunction, closer to how Trekkie settled in English. The two meanings now coexist, and a speaker's intent depends entirely on which side of the Pacific they learned the word on.
Japanese dictionaries record the domestic sense; Western fan usage is documented by the borrowing itself. This glossary uses the term descriptively, as a word with two documented lives, and the site's quizzes never use it as a label for readers.
In use"At home in Japan, calling a stranger an otaku is an insult; at an overseas convention, it is printed on the badge."