The fair use principle allows users to use copyrighted material without permission under certain circumstances. If a use is fair, the user does not need to inform or ask permission from the copyright holder.
According to Section 107 of The Copyright Act, there are 4 factors to consider in determining whether a use is fair. They are as follows:
1. the "purpose and character of the use, including whether the use is of a commercial nature or is for nonprofit educational purposes"
2. the nature of the work that is copyrighted
3. the "amount and substantiality of the portion used in relation to the copyrighted work as a whole"
4. the "effect of the use upon the potential market for or value of the copyrighted work."
Quoted material from the U.S. Copyright Office Fair Use Index.
The Checklist and this introduction is licensed by a Creative Commons Attribution License with attribution to the original creators of the checklist Kenneth D. Crews (formerly of Columbia University) and Dwayne K. Buttler (University of Louisville). Used under a CC BY/NC license from Copyright Advisory Services of Columbia University.
Fair Use Checklist
Best Practices for Fair Use A library of best practices in fair use for a variety of resource types and formats
... the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include—
(1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of the copyrighted work.
The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.
From Copyright Law of the United States (title 17) Chapter 1, Section 107 [which is in the public domain because the law is in the public domain!]