http://en.wikipedia.org/wiki/Fan_(person)#Fanboy.2Ffangirl
Fanboy is a term used to describe a male who is highly devoted and biased in opinion towards a single subject or hobby within a given field. Fanboy-ism is often prevalent in a field of products, brands or universe of characters where very few competitors (or enemies in fiction, such as comics) exist.
The term fangirl can be used to describe a female member of a fandom community (counterpart to the masculine "fanboy"😉. Fangirls may be more devoted to emotional and romantic aspects of their fandom, especially (relation-)shipping. However, it is commonly used in a derogatory sense to describe a girl's obsession with something, most commonly a male teen idol or an aspect of Japanese pop culture. Fangirl behavior can vary in intensity. On one end of the scale are those that, while harboring a crush on a particular actor or character, are perfectly capable of understanding that the fulfilment of the crush is never going to happen. On the other end are the girls who are said to be obsessive in their claims on a fictional character, even fighting with other fangirls over who 'owns' the character in question.
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