This article was a guest column published in Law360.

By Jay Yates (April 21, 2026)

With apologies to the “bring out your dead” scene from “Monty Python and the Holy Grail,” means-plus-function language for patent claims is not quite dead.

Indeed, recent opinions from the U.S. Court of Appeals for the Federal Circuit — including Abiomed Inc. v. Maquet Cardiovascular LLC on Feb. 9, Magnolia Technologies Inc. v. Kurin Inc. on March 6, and Gramm v. Deere & Co. on March 11 — confirm that means-plus-function claims continue to be drafted, issued, litigated and even infringed.

Although mortally wounded by the U.S. Supreme Court‘s decision in Halliburton Oil Well Cementing Co. v. Walker in 1946, functional claiming got better after Congress enacted Title 35 of the U.S. Code, Section 112(f), as part of the 1952 Patent Act, legislatively overruling the Supreme Court.

To prevent overly broad claims, the statute requires that functional limitations be construed to cover the corresponding structure, material or acts described in the specification and equivalents thereof.

Later, the Federal Circuit dealt additional blows.[1] But such restrictions have proven to be just a flesh wound to means-plus-function language for patent claims, as illustrated by the recent Federal Circuit decisions. However, who would cross this bridge must first answer these questions three.

A Three-Step Analysis for Means-Plus-Function

1. Does the claim language invoke Section 112(f)?

The first step of a Section 112(f) analysis is to determine whether the claim term at issue is in means-plus-function format. If the claims use the term “means” there is a presumption invoking Section 112(f). However, the Federal Circuit will also construe a claim element as a means-plus-function term even when the word “means” is absent, consistent with the trend beginning with Williamson.

For example, in Magnolia v. Kurin, the Federal Circuit held, affirming the U.S. District Court for the District of Delaware, that without additional structure, claim 1 is alone insufficient to perform its directing function, rebutting the presumption that claim 1’s lack of the word “means” does not invoke Section 112(f). That is, the term “diverter” would not be understood by a person of ordinary skill to have a sufficiently definite structural meaning, but rather as a generic term that captures any structure that performs that function. Hence, “diverter” invokes Section 112(f).

Similarly, in Fintiv Inc. v. PayPal Holdings Inc. last year, the Federal Circuit held, affirming the U.S. District Court for the Western District of Texas, that various “payment handler” terms invoke Section 112(f) because the “payment handler” terms recite function without reciting sufficient structure for performing that function. The “payment handler” terms include:

• A “payment handler service” operable to use [application programming interfaces, or APIs] of different payment processors including one or more APIs of banks, credit and debit cards processors, bill payment processors;
• A “payment handler” configured to use APIs of different payment processors including one or more APIs of banks, credit and debit cards processors, and bill payment processors; and
• A “payment handler” that exposes a common API for interacting with different payment processors.

Thus, the “payment handler” terms invoke Section 112(f).

Likewise, in Optis Cellular Technology LLC v. Apple Inc. last year, the Federal Circuit held, reversing the U.S. District Court for the Eastern District of Texas, that “selecting unit” invokes Section 112(f). The Federal Circuit explained that the word “unit” does not sufficiently connote structure and is similar to other terms that the Federal Circuit has held to be nonce terms similar to “means” and invoke Section 112(f). The Federal Circuit further explained that the term modifying “unit” (i.e., “selecting”) and the surrounding terms (i.e., “configured to randomly select”) are functional and do not supply a sufficiently definite structure.

Consistently, in Abiomed v. Maquet in February, the Federal Circuit held that the U.S. District Court for the District of Massachusetts did not err in determining that “guide mechanism” invokes Section 112(f) because the term does not recite sufficiently definite structure. That is, a skilled artisan would not understand the claimed “guide mechanism” to have a sufficiently definite meaning as the name for a structure.

In In re: McFadden last year, the Federal Circuit held that the Patent Trial and Appel Board did not err in determining that the term “subsystem” as used in the claims is not a term of art that conveys a particular structure to a person of ordinary skill, but is a term devoid of particular structure to be properly understood as being written in means-plus-function format. Thus, the “subsystem” term invokes Section 112(f).

2. If the claim language invokes Section 112(f), what structure, if any, disclosed in the specification corresponds to the claimed function?

The second step of a Section 112(f) analysis is to determine whether the specification discloses adequate corresponding structure. If no structure is disclosed, the claims are indefinite.

In Fintiv, having held that that various “payment handler” terms invoke Section 112(f), the Federal Circuit further held the claims to be indefinite because the specifications do not provide additional disclosures other than reciting the function of the “payment handler” terms using generic terms without providing any details about an algorithm to carry out the functions of using APIs of different payment processors including one or more APIs of banks, credit and debit cards processors, bill payment processors, and exposing a common API for interacting with different payment processors. That is, without an algorithm to achieve these functionalities — and, more generally, given the specifications’ failure to disclose adequate corresponding structure — the Federal Circuit held the “payment handler” terms to be indefinite.

In Gramm v. Deere & Co. in March, the parties agreed that “control means” is a means-plus-function limitation that invokes Section 112(f), but disputed whether the specification’s disclosure of the “head controller 20” feature of the corresponding structure is sufficiently definite. Expert testimony established that, as of 1997, a skilled artisan would have known there were three commercially available head controllers used in Deere combines — Dial-A-Matic Versions #1, #2, and #3.

The Federal Circuit found that the U.S. District Court for the Southern District of Iowa did not clearly err by determining the Dial-A-Matic Versions #2 and #3 use microprocessors to control header height and therefore require an algorithm to avoid indefiniteness. However, Dial-A-Matic Version #1 was commercially available as of 1997 and uses logic circuitry — not a microprocessor — to raise and lower the header. The Federal Circuit held that, under its precedent, the Dial-A-Matic Version #1 is therefore not a general-purpose computer and does not trigger the algorithm requirement. The Federal Circuit reversed the district court’s conclusion of indefiniteness for the “control means” term and judgment of invalidity for remand to the district court.

In McFadden, having held that the “subsystem” term invokes Section 112(f), the Federal Circuit determined that the specification discloses structure that corresponds to the recited subsystem — i.e., a computer system running software — identifying various different structures in the specification that can operate as the computer system/subsystem and further identifying the disclosure that the computer system/subsystem uses a decision matrix 70 to determine if an information item should be included.

Consistently, in Optis Cellular, after determining that “selecting unit” invokes Section 112(f), the Federal Circuit remanded the second step of the Section 112(f) analysis to the district court.

3. Is the accused structure the same or equivalent to the disclosed corresponding structure?

The third step of a Section 112(f) analysis is to determine infringement, namely, whether the accused structure is the same as the disclosed structure or is an equivalent under Section 112(f), i.e., (1) by showing it performs the identical function, and (2) is otherwise insubstantially different with respect to structure.

In Abiomed, the Federal Circuit affirmed summary judgment of noninfringement when the patent owner’s expert never identified the alleged differences between the accused devices and structure of the district court’s claim construction and never explained why any differences are “insubstantial.”

Similarly, in Genuine Enabling Technology LLC v. Sony Group Corporation in February, the Federal Circuit affirmed summary judgment of no infringement, reasoning that, although case law allows for greater weight to be given to individual components that play a central role in the identified structure, this does not excuse the patent owner’s obligation to account for all the elements of that identified structure and make the case for why certain elements are more central to the infringement analysis than others. Indeed, the Federal Circuit held that the patent owner never supplied any evidence for why many elements of the identified structure should be treated as having little to no weight in the infringement analysis

However, in Steuben Foods Inc. v. Shibuya Hoppmann Corp. last year, the Federal Circuit reversed the U.S. District Court for the District of Delaware’s entry of judgment as a matter of law of noninfringement following a jury verdict of infringement. The district court construed the term “means for filling the aseptically disinfected plurality of bottles at a rate greater than 100 bottles per minute” as a means plus function limitation. The district court identified the function as “[aseptically] filling the aseptically disinfected plurality of bottles at a rate greater than 100 bottles per minute,” and the structure as “filling valves (Items 194A, 194B) and filling nozzles (Items 190A, 190B); a control system (Item 550); a conveyer plate (Item 94); conveyor (Item 106); and equivalents.”

The jury returned a verdict of infringement, but the district court grant JMOL of noninfringement. However, the Federal Circuit held that the patent owner’s expert provided substantial evidence for the jury to find the accused structures perform the claimed function in an equivalent way; the Federal Circuit reversed and reinstated the jury’s verdict of infringement.

As recent Federal Circuit opinions confirm, means-plus-function claims are very much alive.

Jay Yates is a partner at Patterson & Sheridan LLP.

The opinions expressed are those of the author(s) and do not necessarily reflect the views of their employer, its clients, or Portfolio Media Inc., or any of its or their respective affiliates. This article is for general information purposes and is not intended to be and should not be taken as legal advice.

[1] See In re Donaldson, 16 F.3d 1189 (Fed. Cir. 1994) (holding that § 112(f) does not expand the claim scope but rather acts as a restriction); see also Williamson v. Citrix Online, LLC (Fed. Cir. 2015) (removing the strong presumption against applying § 112(f) when the word “means” is absent).