What is Fair Use?
The current copyright law, while giving the owner of the copyright the exclusive right to reproduce and distribute the work, has one exception to these exclusive rights which is called the "fair use exception." The purpose of the fair use exemption was created to allow students, scholars and critics the right to reference a copyrighted work in their own scholarship, teaching and critiques without fear of litigation.
The fair use exception permits the reproduction of portions of copyrighted works without the copyright owner's permission, but only under very limited circumstances. The Fair Use Doctrine was added to the Copyright Act of 1976 and was based on a history of judicial decisions that recognized that unauthorized use of copyrighted materials were "fair uses." Unfortunately Section 107 is not specific, and fair use should be examined on a case by case basis.
While there is no one right answer as to what constitutes "fair use" , there is listed in the copyright law four factors that are meant to guide you in using copyrighted materials. These four factors are considered in all fair use evaluations and you should make a good faith effort to comply with these factors although it is not a simple task.
Section 107 contains a list of the various purposes for which the reproduction of a particular work may be considered fair, such as criticism, comment, news reporting, teaching, scholarship, and research. Section 107 also sets out four factors to be considered in determining whether or not a particular use is fair:
The distinction between fair use and infringement may be unclear and not easily defined. There is no specific number of words, lines, or notes that may safely be taken without permission.
The US Copyright Office provides this fact sheet.
Some guidelines and best practices:
Code of Best Practices in Fair Use for Academic and Research Libraries.
Code of Best Practices in Fair Use for Scholarly Research in Communication. Created by the International Communication Association. Helps U.S. communication scholars to interpret the copyright doctrine of fair use.
Code of Best Practices in Fair Use for Online Video. A code of best practices that helps creators, online providers, copyright holders, and others interested in the making of online video interpret the copyright doctrine of fair use.