Fair use is a concept embedded in U.S. law that recognizes that certain uses of copyright-protected works do not require permission from the copyright holder. (See Title 17, section 107)
Purpose and character of the use Not all noncommercial and nonprofit educational uses are considered fair by courts, but news reporting, criticism and scholarship generally are. There should be a balance between this and the other three factors.
Nature of the copyrighted work Published works, factual or nonfiction based works are better candidates for fair use than those that are unpublished, highly creative (music scores, art work or films), or nonfiction.
Amount of the material used There is no definitive amount to guarantee acceptable use; generally the greater the amount copied, the less likely it is fair use. Using the "heart of the work" or essential portion of the work does not fall under fair use.
Effect of use on the potential market for or value of the work
* Not all uses in an academic context are automatically considered fair use!