Some uses of a copyrighted work are considered ‘fair use’. The use is not legally considered to be an infringement if its use is non-commercial or incidental in nature. There is no single definition of fair use but courts have interpreted it depending on the purpose and character of the use. For example, they may look at whether it was a non-profit use versus commercial use, how much text was copied in relation to the entire work, and the potential market or value of the copyrighted work. Fair use is often legitimate when a work is being used for teaching, research, scholarship, criticism or journalism. You can also quote within reasonable limits from other work without prior agreement, provided that the source is given and the text is not presented out of context.