To be definite, a valid patent claim must “inform those skilled in the art about the scope of the invention with reasonable certainty.” Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 910 (2014). 

Language of degree, such as “unobtrusive” or “aesthetically pleasing,” is indefinite unless, “when read in light of the specification and the prosecution history, [it] provide[s] objective boundaries for those of skill in the art.” Interval Licensing LLC v. AOL, Inc., 766 F.3d 1364, 1371 (Fed. Cir. 2014) (requiring more than identifying “some standard” of measure); see also Datamize LLC v. Plumtree Software, Inc., 417 F.3d 1342, 1350–51 (Fed. Cir. 2005). 

A claim term, even if it refers to certain objective measures, is indefinite if it “might mean several different things [but] no informed and confident choice is available among the contending definitions.” Interval Licensing, 766 F.3d at 1371 (quoting Nautilus, 572 U.S. at 911 n.8). 

In Akamai Technologies, Inc. v. MediaPointe, Inc., No. 2024-1571, __ F.4th __ (Fed. Cir. Nov. 25, 2025), the Federal Circuit affirmed that patent claims were invalid for indefiniteness because the claim limitations “optimal” and “best” were terms of degree where the specification did not provide objective boundaries for their measure.

While the specification teaches various criteria “may be relevant to the analysis of which nodes or routes are best, but it does not explain which factors ought to be considered or how to balance them.” Citing Interval Licensing, 766 F.3d at 1373, the Court held that this did not provide “a reasonably clear and exclusive definition” of “optimal” or “best,” emphasizing the need for the measure to be “exclusive.” 

     We have repeatedly said that when “multiple methods” for determining whether a claim limitation is met “lead[ ] to different results without guidance . . . as to which method should be used,” the claim is indefinite. Dow Chemical Co. v. Nova Chemicals Corp. (Canada), 803 F.3d 620, 634 (Fed. Cir. 2015); see Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 789 F.3d 1335, 1344–45 (Fed. Cir. 2015).

The Federal Circuit also noted that if the terms “optimal” and “best” add nothing to the claim, that would be “a disfavored result,” citing Bicon, Inc. v. Straumann Co., 441 F.3d 945, 950–51 (Fed. Cir. 2006) (“[C]laims are interpreted with an eye toward giving effect to all terms.”) (collecting cases).