Fair use is a right granted to the public for limited use of copyrighted material without obtaining permission from the rights holder, for such purposes as scholarship, review, education, entertainment, and parody.
No bright lines separate fair use from copyright infringement
Fair use takes precedence over the author's interest and is a defense against copyright infringement. However, it’s important to note that the assertion of fair use will typically come after an accusation of copyright infringement, and the final decision of whether a use constitutes fair use or not is made by a court.
Courts use four criteria in judging whether a use is “fair” or infringes a copyright:
If you’re unsure that your use of copyrighted materials constitutes fair use, consider taking the extra step of seeking permission from the rights holder, rather than finding yourself or your institution defending against a charge of copyright infringement.
Here's a fair-use checklist Cornell University has developed for students and faculty.
See also Reproduction of Copyrighted Works by Educators and Librarians, an excellent 24-page booklet from the U.S. Copyright Office that covers most of the thorny questions educators have about fair use.
This work is licensed under a Creative Commons Attribution 3.0 Unported License.