What Is “About” About? How Courts Interpret One of Patent Law’s Most Deceptively Simple Words

What Is “About” About? How Courts Interpret One of Patent Law’s Most Deceptively Simple Words

Patent practitioners often treat the word “about” as a convenient drafting tool. It provides flexibility, avoids undue precision, and can help account for real-world manufacturing and testing variation. But when patents are litigated, the seemingly simple word “about” can become the focus of a significant claim construction dispute.

While the Federal Circuit has generally found that “about” means approximately, its precise scope depends heavily on the patent’s specification, prosecution history, prior art, and the underlying technology.

The General Rule: “About” Means Approximately

In the leading case, Merck & Co. v. Teva Pharmaceuticals USA, Inc.,[1] the Federal Circuit addressed a claim directed to a method of treating osteoporosis using “about 70 mg of alendronate monosodium trihydrate.”

The district court interpreted this claim language narrowly, effectively construing “about 70 mg” to mean exactly 70 mg based on language in the specification that clarified the weight basis for dosage amounts due to mixed nomenclature in the art. Based on the narrowed claim language, the district court concluded that the patent was neither anticipated nor rendered obvious by the prior art.

On appeal, however, the Federal Circuit reversed. The court emphasized that the ordinary meaning of “about” is approximately and found that the specification did not clearly redefine the term. Although the specification contained language describing precise dosage amounts near the term “about,” the court found that Merck had not clearly redefined the term due to repeated use of “about” in its ordinary sense throughout the disclosure. Moreover, the Federal Circuit noted that a narrower construction would render portions of the claim language superfluous. As a result, “about” retained its ordinary meaning, broadening the claim, and the claims at issue were ultimately found obvious.

 Merck  is a prime example of the difficulties  a patentee may face when attempting to assign a special definition to “about.” Absent a clear, explicit, and consistently used redefinition in the specification, courts are likely to construe the term according to its ordinary meaning: approximately.

Where Does “About” End?

If “about” means approximately, then how far does the scope of the approximation extend?

The Federal Circuit addressed this issue in Pall Corp. v. Micron Separations, Inc.[2] The claims covered a membrane having a CH₂:NHCO ratio within the range of “about 5:1 to about 7:1.” The accused product used nylon 46, which had a ratio of approximately 4:1.[3]

The district court found no literal infringement but found infringement under the doctrine of equivalents. The Federal Circuit affirmed.

Critically, the court explained that the meaning of “about” does not have a universal definition. Instead, its scope depends on the technological circumstances of the particular invention. In this case, the Federal Circuit agreed with the district court’s analysis of evidence found within the specification and extrinsic evidence. The specification disclosed a specific example ratio, 5.3:1, which was considered as evidence bearing on the practical range of the claimed scope. The inventor’s testimony at trial was also considered, and the inventor stated that he had tried a 3:1 ratio but found it unsatisfactory as a material and that he had set the 5:1 ratio as the lower bound due to commercially available nylons.[4]

Based on this evidence, the court concluded that a 4:1 ratio fell outside the literal scope of the claimed range, even though the claim used the modifier “about,” but agreed with the lower court that the product infringed under the doctrine of equivalents.

The Role of Prosecution History

Although Pall illustrates how technical evidence may define the scope of “about,” prosecution history can also significantly influence those boundaries. In Pall, the court found that the inventor’s response to a § 112 action did not amount to surrendering the 4:1 ratio.[5]  Statements made to distinguish from prior art during prosecution, however, may give rise to prosecution disclaimer or estoppel arguments.

For example, in Modine Manufacturing Co. v. U.S. International Trade Commission,[6][7] the claim involved condenser fins described as having “a relatively small” thickness. The International Trade Commission construed this to mean, based on the specification, a range of “about 0.015-0.040 inches.” During prosecution, the applicant narrowed an originally broader range because prior art disclosed thicknesses of approximately 0.0496 inches.

On appeal, the Federal Circuit rejected the argument that the upper limit should be fixed at exactly 0.040 inches. Nevertheless, the court recognized that the prior art reference limits the outer boundary of about 0.040 inches to 0.0496 inches. The case was remanded so that the scope of the range could be determined.

Case Summary: Small words, Big consequences

These cases are illustrative of the nuances and impact of using open ended terms like “about” or “relatively” in patent drafting and prosecution. When utilizing such terms patent prosecutors must consider its usage throughout the specification, its context within the claims, the degree of variation within the art, and why the inventors themselves may not have been as precise. Further, the ambiguity of “about” is a double edge sword to those asserting their patents because an accused infringer may attempt to broaden the scope of the patent to render it unenforceable due to prior art or narrow the scope of the patent to render the accused infringer outside of the scope of the patent.

It is critical that intellectual property attorneys discuss, weigh, and communicate the impact of such seemingly simple word choices to their clients, so that their inventions are properly protected and can survive whatever litigation challenges may be thrown their way.

[1] Merck & Co., Inc. v. Teva Pharmaceuticals USA Inc., 365 F.3d 1364 (Fed. Cir. 2005).

[2] Pall Corp. v. Micron Separations, Inc., 66 F.3d 1211, 1217 (Fed. Cir. 1995).

[3] Nylon 66, with a ratio of 5:1, was also at issue in this case and was found to have literally infringed but is outside the scope of this blog post.

[4] No testing had been performed between 5:1 and 3:1 because of the lack of commercially available nylons.

[5] The inventor had responded to the § 112 rejection that the range was “actually rather narrow” and that it excluded the vast majority of resins.

[6] Modine Mfg. Co. v. U.S. Int’l Trade Comm’n, 75 F.3d 1545 (Fed. Cir. 1996), abrogated by Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558 (Fed. Cir. 2000).

[7] Although portions of Modine were later abrogated by the Federal Circuit’s en banc decision in Festo, courts have continued to cite aspects of the analysis relating to claim scope and approximation ranges. As a result, the law remains somewhat unsettled in this area.