doctrine of equivalents

The doctrine of equivalents is a legal rule in most of the world's patent systems that allows a court to hold a party liable for patent infringement even though the infringing device or process does not fall within the literal scope of a patent claim, but nevertheless is equivalent to the claimed invention. U.S. judge Learned Hand has described its purpose as being "to temper unsparing logic and prevent an infringer from stealing the benefit of the invention". Royal Typewriter Co. v. Remington Rand, Inc., 168 F.2d 691, 692 (2d Cir. 1948).
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a judicially created theory for finding patent infringement when the accused process or product falls outside the literal scope of the patent claims. The essential objective inquiry is: “Does the accused product or process contain elements identical or equivalent to each claimed element of the patented invention?”

-- see MPEP 2186 for more

Context: Patent

Patent. 1. The accused product, process, apparatus, or composition: a. has substantially the same overall function, b. operates in substantially the same way, and c. achieves substantially the same result or qualities as the product, process, apparatus, composition disclosed in the patent claim; and

2. Every element of the patent claim either is literally present, or has some substantially equivalent corresponding element in the accused product process apparatus composition.