Substantial Similarity Law and Legal Definition

Under copyright law, substantial similarity refers to a strong resemblance between a copyrighted work and an alleged infringement. Thereby, it creates an inference of unauthorized copying. The standard for substantial similarity is whether an ordinary person would conclude that the alleged infringement has appropriated nontrivial amounts of the copyrighted work’s expression.

Substantial similarity is considered to be an appropriate test for infringement. It is also called ordinary observer test, whereby, it determines whether an average lay observer would recognize the alleged copy as having been appropriated from the copyrighted work.[Cameron Indus. v. Mother's Work, Inc., 338 Fed. Appx. 69, 70 (2d Cir. N.Y. 2009)].