Fair Use allows limited use of copyrighted materials under certain circumstances without getting permission from the copyright holder. It is usually used for educational purposes. The four factors to be considered for determining Fair Use are:
The purpose and character of the use, including whether such use is of commercial nature or is for nonprofit educational purposes
The nature of the copyrighted work
The amount and substantiality of the portion used in relation to the copyrighted work as a whole
The effect of the use upon the potential market for, or value of, the copyrighted work