Key Takeaway: The term “about” remains useful in biotech and pharmaceutical claims, but only if the patent provides objective guidance about what the term means. Absent that guidance, “about” may render the claims indefinite. Applicants may consider: (i) expressly defining “about” in the specification; and (ii) including precise numerical ranges in dependent claims to provide clearer fallback positions.
Many biotech and pharmaceutical patent claims include the term “about” to provide added breadth of claim interpretation in connection with values or numerical ranges. In Enviro Tech Chemical Services, Inc. v. Safe Foods Corp., the Federal Circuit affirmed that terms of approximation such as “about” are not inherently indefinite, but such terms must still provide a skilled artisan with reasonable certainty as to claim scope.[1]
Enviro Tech Chemical Services, Inc.’s (Enviro Tech’s) patent involved methods of treating poultry using peracetic acid solutions. The district court held the asserted claims invalid as indefinite, finding that the terms “about” and “antimicrobial amount” failed to provide sufficient clarity as to claim scope. The Federal Circuit affirmed, focusing solely on the term “about.” The Federal Circuit explained that although terms of approximation can be permissible, those terms must be anchored by guidance in the claims, specification, or prosecution history. Here, the claims recited a pH range of “about 7.6 to about 10” but provided no indication of acceptable deviation. The specification likewise included some examples with a ±0.3 pH threshold for “about,” while other examples permitted larger deviations, and so failed to resolve the ambiguity. The prosecution history compounded the problem, as the applicant used the term inconsistently and never defined its scope.
On appeal, Enviro Tech argued that amendments narrowing the lower endpoint from “about 7.3” to “about 7.6” implied a ±0.3 limitation, but the Federal Circuit rejected that position because the prosecution history lacked any clear statements supporting such an interpretation.[2] The Federal Circuit also noted the claimed pH range had been amended to distinguish prior art close to the claimed boundary. In that context, the Federal Circuit suggested that greater precision was required, remarking that the prior art was “almost ‘about’ a pH of 7.6.”[3]
The Federal Circuit reiterated that patent claims must inform those skilled in the art of their scope with “reasonable certainty.”[4] The court further explained that although terms of approximation such as “about” and “approximately” are not inherently indefinite, they must provide reasonably certain boundaries in light of the “technological facts of the particular case.”[5] And where the specification and prosecution history fail to provide any consistent indication of the claimed range, approximation language may render the claims indefinite.[6] Applying those principles, the Federal Circuit concluded that the intrinsic record supplied no objective or consistent standard for the scope of “about,” leaving a skilled artisan unable to determine the claimed pH range with reasonable certainty and rendering the asserted claims indefinite.
Although Enviro Tech arose in the context of poultry processing, the decision has implications for biotechnology and pharmaceutical patent claims. Approximation terms routinely appear in claims directed to, inter alia, dosage ranges, concentrations, purity levels, binding affinities, particle sizes, and biological activity.
One practical lesson is that variability in experimental data can create indefiniteness problems if the patent application specification does not explain how that variability relates to claim scope. Different studies or embodiments may naturally produce different tolerances, particularly in biological systems. Where different tolerances appear in different experiments, for example, it may be helpful to provide some explanatory disclosure to attempt to reconcile the variation(s). Applicants may also consider including precise numerical ranges in dependent claims to provide fallback positions if broader approximation language (like the word “about”) is later challenged.
Editor: Brenden S. Gingrich, Ph.D.
[1] Enviro Tech Chem. Servs., Inc. v. Safe Foods Corp., No. 2024-2160, slip op. at 4–5 (Fed. Cir. May 4, 2026).
[2] Id. at 7.
[3] Id. at 7–8.
[4] Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 901 (2014).
[5] Ortho-McNeil Pharm., Inc. v. Caraco Pharm. Lab’ys, Ltd., 476 F.3d 1321, 1326 (Fed. Cir. 2007); see also Interval Licensing LLC v. AOL, Inc., 766 F.3d 1364, 1370-72 (Fed. Cir. 2014).
[6] Amgen, Inc. v. Chugai Pharm. Co., 927 F.2d 1200, 1218 (Fed. Cir. 1991).
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