Fair use is a legal doctrine that permits limited use of copyrighted material without acquiring permission from the rights holders. It is one type of limitation and exception to the exclusive rights copyright law grants to the author of a creative work. Examples of fair use in United States copyright law include commentary, search engines, criticism, parody, news reporting, research, teaching, library archiving and scholarship. It provides for the legal, unlicensed citation or incorporation of copyrighted material in another author's work under a four-factor balancing test.