'''Common usage:''' 

A ''nickname'' is a shortened or familiar form of a person's proper name.

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'''Internet chat and Usenet usage:'''

The term ''nickname'' refers to an alias or handle used to identify someone online, and may have little relation to their proper name.

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'''Usage on this Wiki:'''

On this wiki, RealName''''''s are preferred and the norm. A common-usage nickname may qualify as a "real name", but an alias does not. 

(See RealNamesPleaseDiscussion if you want to argue about it.)

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'''InterWiki usage:'''

Also used in inter-wiki as prefix to a wiki site - 'c2:Recent''''''Changes' with the 'c2:' being the nickname for 'h''''''ttp://c2.com/cgi/wiki?'.