The Court of Appeals for the Federal Circuit, in Nature Simulation Systems Inc. v. Autodesk, Inc., No. 2020-2257 (Fed. Cir. Jan. 27, 2022), reversed the Northern District of California’s determination that limitations within Nature Simulation Systems’ claims lacked definiteness because there were unanswered questions about the limitations that were not answered in “the claim language, standing alone.” The CAFC explained that the district court applied an improper standard for determining definiteness and that the proper standard should include a review of the intrinsic record of the patent document, including “the words of the claims themselves, the remainder of the specification, the prosecution history, and extrinsic evidence concerning relevant scientific principles, the meaning of technical terms, and the state of the art.” After applying the proper standard, the CAFC found the challenged limitations definite.