Some authors use fictional languages
as a device to underline differences in culture, by having their characters communicate in a fashion which is both alien and dislocated. Primary examples of this are:
Some of these languages are presented as distorted versions of modern English
. Jack Womack's Dryco novels feature a future form of English with a modified grammar.
A fictional language is separated from an artlang (language constructed for beauty or fun) by both purpose and relative completion: a fictional language generally has the least amount of grammar and vocabulary possible, and it is made usually for a novel or movie.
Others have developed languages in detail for their own sake, such as
the languages of Middle-earth of J. R. R. Tolkien, Star Trek's Klingon and the languages in Star Wars.