The "fair use" defense against copyright infringement:

Question

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The copyright act sets out four factors for evaluating whether a use is a fair use: (1)purpose and character of the use (commercial uses are presumptively unfair); (2)nature of the copyrighted work (the scope of fair use is greater for informational work than for creative work); (3)amount and substantiality of portions used (fair use may apply if there are substantial differences between the copyrighted work and the derivative work); and (4)effect on the market (fair use does not apply if the use diminishes the value or marketability of the original work).

The "Fair Use" Defense Against Copyright Infringement