The Fair Use Exception
One may make fair use of a copyrighted work without the copyright holder’s permission. The determination of whether a use of a copyrighted work is within fair use depends upon making a reasoned and balanced application of the four fair use factors set forth in Section 107 of the U.S. Copyright Act. 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.