It is a word that has it's root in costume play. It is both a noun and a verb.Cosplay can mean the actual costume, as well as the action of wearing it Contrary to popular belief, many cosplayers (well over 98%) do not believe they are the characters they are "cosplaying" as. Cosplays are typically worn to anime conventions. Cosplays are made for the following reasons..

1.) To recreate a 2 dimensional art form into 3-D.
2.) To challenge one's self to create a cosplay. Many of which dont seem possible to physically create, but somehow are.
3.) To show appreciation and/or interest in a certain anime/manga/videogame.
4.) To take pride in a cosplay that looks well done.
5.) Because normal cloth that is shitted out for everyone via mass factories
and little kids in china are dull. Cosplays are much more interesting to
wear. And each cosplay is one of a kind unique considering the wearer
most likely made it him/herself.
6.)It's a Hobby


Reasons why cosplays are worn:
1.) To take pride in ones own creation
2.) To wear something out of the ordinary (societies restrictions on what is allowable to be worn everyday is bland)
3.) To show support and/or interest in an anime/manga/videogame
4.) Self expression. Often the character that is choosen to be cosplayed
mirrors the actual person wearing the cosplay. The person's personality is
like the character Not the other way around (the person wants to be
the character).
5.) To get into the spirit of the son
6.) To have fun

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Cosplayers cosplay for the same reasons that...
1.)Sports fans wear jersies and paint themselves for games.
2.)Goths wear all black, punk wear punk cloth, Preps wear tight cloth, "gangstas" wear baggy cloth....
But for cosplayers....A cosplay is worn for 1-3 days out of the year.
A limited and restrained form of self expression.
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Cosplay is a "HOBBY". Much like a model builder builds models, a person modifies their car, a hunter hunts (when they can buy food instead), a gamer plays games, a sports fan watches sports. A cosplayer cosplays (makes costumes).