Simple English definitions for legal terms
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Substantial similarity refers to how much one thing looks or sounds like another thing that is protected by a trademark or copyright. If something is too similar to a protected work, it may be considered infringement. The level of similarity needed to be considered infringement depends on the product and how careful the typical buyer would be in choosing it. For example, someone buying a watch would be expected to be more careful than someone buying candy. There are different types of similarity, such as comprehensive nonliteral similarity, which means copying the general ideas or structure of a work, and fragmented literal similarity, which means copying exact words or phrases. Substantial similarity is a strong resemblance between a protected work and an alleged infringement, which creates an inference of unauthorized copying.
Definition: Substantial similarity refers to the resemblance of one trademark or copyrighted work to another. It is a question of overall impression rather than an element-by-element comparison of the two marks.
For example, if a company creates a logo that is very similar to another company's logo, it may be considered substantial similarity. The standard for substantial similarity depends on the nature of the product and how much care the typical buyer would be expected to take in making the selection in that particular market.
In copyright law, substantial similarity can refer to both comprehensive nonliteral similarity and fragmented literal similarity. Comprehensive nonliteral similarity is when there is similarity in the general ideas or structure of a work, such as a movie's plot, without using the precise words or phrases of the work. Fragmented literal similarity is when there is similarity in verbatim portions of the protected work.
The standard for substantial similarity in copyright law is whether an ordinary person would conclude that the alleged infringement has appropriated nontrivial amounts of the copyrighted work's expressions. For example, if a book is copied almost word-for-word by another author, it may be considered substantial similarity.