Copyright is meant to protect the rights of creators and to encourage the creation of science and scholarship. In most cases, you must ask permission of the copyright holder to use his or her work, but there are limitations and exceptions to copyright law. You do not need to request permission of the copyright holder if your use of a work is considered a "fair use."
Section 107 of the U.S. Copyright Law says that the fair use of a copyrighted work "for purpose such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research" does not infringe on copyright.
To determine whether your use of an item is fair, you'll need to consider the four factors of fair use and do a fair use analysis.
Isn't educational use the same as fair use?
Unfortunately, it isn't. Using an item for an educational purpose weighs in favor of fair use for the first factor, but you must consider all four factors to make a fair use determination.
Is it always fair use to use 10% or less of a work?
No. Copyright law does not provide a percentage that would constitute fair use. Generally, the smaller the amount used, the more likely it is that the use is fair. However, the other factors must also be considered.
Factor 1: Purpose and character of the use
For what reason (educational/non-profit/commercial) will the work be used?
Personal, non-profit, and educational use often weighs in favor of fair use.
Is the work being used for parody, commentary, or criticism?
Use of the work for a new purpose or in a new way weighs in favor of fair use.
Is the work being used to create something new or add value to the original?
If your use of a work is "transformative," you can more likely claim fair use than if you were to simply copy it.
Factor 2: Nature of the work
Does the work contain facts (like a biography) or is it imaginative (like a novel)?
Use of fact-based works is more likely to be considered fair than use of creative works.
Is the work published or unpublished?
Use of published works favors fair use; use of unpublished works does not favor fair use.
Factor 3: Amount of the copyrighted work used
What amount of the work do you want to use?
There are no clear guidelines for what amount of a work constitutes fair use; it must be considered in relation to the whole. In general, the less used, the more likely you can claim fair use.
The Agreement on Guidelines for Classroom Copying in Not-for-Profit Educational Institutions provides minimum standards for educational fair use.
Is the amount you want to use the "heart" of the work?
Use of the defining or signature part of a work weighs against fair use.
Are you using only what is absolutely necessary?
The less used, the more likely you can claim fair use.
Factor 4: Effect of the use upon the market
Will your use of the work cause the copyright owner to lose income?
If your use prevents people from purchasing the copyright holder's work, it is difficult to argue fair use. For instance, if this use replaces a coursepack that students otherwise would be required to purchase, you would have a difficult time claiming fair use.
Have you used this item in previous semesters?
If you have used the item in previous semesters without getting permission, it is difficult to claim fair use, because repeated use of an item without permission may have an effect upon the market.
Is there a way to get permission to use the work?
The easier it is to get permission from the copyright holder, the harder it is to claim fair use. If you have been unsuccessful contacting the copyright holder, (as you might in the case of orphan works), you can more easily claim fair use.