Legal Definitions - substantial similarity

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.