Fair Use

What is fair use?
Fair use is a part of copyright law that allows you to use copyrighted material under certain circumstances without permission from the copyright holder.

What qualifies as fair use?
There are four factors that constitute fair use. All four factors must be met for something to be considered fair use:

Purpose and character - how is the copyright material being used? Fair use favors nonprofit and educational use over commercial use.
Nature of the work - the type of work being used plays a role in determining if it's considered fair use or not.
Amount used - how much of the copyright material is being used? A small amount of the work is more likely to be considered fair use; however there are exceptions if a small amount is considered to be the heart of the work.
Market effect - how does the use of copyright material effect the owner's ability to make money from it? The more conservative the use, the more likely it will be considered fair use.