Proving the second element of copyright infringement, copying of protected subject matter, is just as important as proving access and substantial similarity. However, would-be plaintiffs often gloss over this requirement in the mistaken assumption that any copying is sufficient to support an infringement suit. To understand what constitutes copying of protected expression, you must consider what elements of your work are not protected. And, as discussed earlier, there are several categories of elements of copyrightable works, some of them important to the overall quality of a work that aren't protected by copyright. If you review the list of exceptions to the general rule that copyright protects what you create, you can better apply the second part of the test for copyright infringement.
Substantial similarity is hard to define.
Although it's not possible to pinpoint the border between infringing and non-infringing similarity, a map of the danger zone between the two exists from copyright case law. To prove substantial similarity, plaintiffs do not have to demonstrate that the defendants' works are nearly identical to their own works. However, courts will not interpret even several small, unimportant similarities between the works in question as a substantial similarity. If so, substantial similarity exists. Examples of substantial similarity Some examples of actions that will always result in infringement will help you grasp the difficult concept of substantial similarity.