If I'm using something for an educational purpose, I don't have to worry about copyright, right?
What if I'm only using a little bit of a work? Is that okay?
Actually, it's not that simple. There is no one criterion that makes a use "fair". Copyright law does allow that in some situations a person may not need to get permission to use a work created by someone else. Those situations are governed by four factors: purpose of the intended use, nature of the work being used, amount of the original work being used, and the effect of the use on the market for the original. All four factors must be evaluated in each case to determine whether permission is needed before using the work.
The links on the left of this guide will help you evaluate your intended use.
Just because you don't see a copyright symbol, that does not mean a work is free to use. Always assume a work is under copyright until you can prove otherwise.