Section 107 of U.S. Copyright Law allows for some uses of portions of copyrighted works for purposes such as criticism, comment, news reporting, teaching, scholarship, and research.
Determining Fair Use is done on a case-by-case basis according to the Four Factors of Fair Use:
- Purpose of use
- Nature of the original work
- Amount or portion used
- Effect of the use on potential market/value of the work
Each of these factors must be considered and balanced with the others to gain an overall picture of your intended use and to help you reach an informed decision.