Doctrine of Equivalents Law and Legal Definition

The doctrine of equivalents is a judicially created doctrine of patent law. If one makes a minor departure from the patent claim and, therefore, does not literally infringe, one may nevertheless be held to be an infringer if one achieves substantially the same function in substantially the same way to obtain substantially the same result.

This results from an equitable balancing of interests, leading to the conclusion that one who makes an insubstantial change should not be permitted to obtain the benefit of the invention while avoiding infringement. The doctrine of equivalents allows a patent owner to prove infringement even when the claims are not literally infringed.