The rule of addition applies when someone creates a replication of an item already patented but adds some sort of extra feature or improvement.That new extra-feature item will not be considered a patent infringement.

Question

Quizplus · Accepted Answer

The rule of addition does not automatically exempt a new product from being considered a patent infringement. If the new product incorporates the patented invention and adds new features, it may still infringe the original patent unless the addition is non-obvious and sufficiently inventive to warrant its own patent.

The Rule of Addition Applies When Someone Creates a Replication