According to the Standford University Libraries, fair use is “any copying of copyrighted material done for a limited and “transformative” purpose, such as to comment upon, criticize, or parody a copyrighted work.” 

The tricky thing about fair use is that there are no hard and fast rules that creators can follow to be sure their use can be considered fair use. The measure of determining if something is fair use is if it is determined to be so in a court case, at which point people using the work may have a lot to lose.

There are 4 factors that people can use to determine if their use of a work is likely to be considered fair use:

1. purpose of the use
2. nature of the copyrighted material
3. effect on the market for the original, and
4. amount copied