The exclusive rights of a copyright owner are not unlimited. One of the most important limitations on exclusive rights is the doctrine of "Fair Use," which permits limited copying of a copyrighted work for educational or research purposes.
Under the Copyright Law, "Fair Use" of a copyrighted work for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is allowed and is not an infringement of copyright. In determining whether the use made of a work in any particular case is fair use, the factors to be considered include:
The fair use exception is purposefully broad and flexible. Each factor is relevant in order to determine whether a particular use is a fair use. A final determination on fair use depends on weighing and balancing all four factors against the facts of an individual situation. Items in the public domain may always be used.