There is no precise definition of “fair use;” rather the law lists certain factors that must be considered in order to determine whether a particular use is fair. Those factors are:
* the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; * the nature of the copyrighted work; * the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and * the effect of the use upon the potential market for or value of the copyrighted work.
Some examples of “fair use” are:
* a quotation of excerpts in a review or criticism for purposes of illustration or comment; * a quotation of short passages in a scholarly or technical work, for illustration or clarification of the author's observations; or * a reproduction by a teacher or student of a small part of a work to illustrate a lesson.
Remember, there is no blanket exemption for educational and scholarly purposes.
A useful checklist to apply the Fair Use Doctrine is linked here.
A useful set of guidelines to assist in applying the Fair Use Doctrine for classroom copying with respect to books and periodicals is linked here.
The following external links discuss the Fair Use Doctrine:
The U.S. Copyright Office
The Copyright Clearance Center
CETUS (Consortium for Educational Technology in University System)
CONFU Final Report (Conference on Fair Use)
CCUMC (The Consortium of College and University Media Centers)
University of Texas System (Office of General Counsel)