In a patent, the patentee is free to choose a broad term and expect to obtain the full scope of its plain and ordinary meaning unless the patentee clearly redefines the term (lexicography) or disavows claim scope (claim disavowal). Thorner v. Sony Comput. Ent. Am. LLC, 669 F.3d 1362, 1367 (Fed. Cir. 2012). To act as his own lexicographer, “a patentee must clearly set forth a definition of the disputed claim term other than its plain and ordinary meaning.” Id. at 1365 (citation modified). The court will look for “clear lexicography.” Id. at 1366. 

A patent specification may define claim terms “by implication” such that the meaning may be found in or ascertained by a reading of the patent documents. Bell Atl. Network Servs., Inc. v. Covad Commc'ns Grp., Inc., 262 F.3d 1258, 1268 (Fed. Cir. 2001). But such “implied redefinition must be so clear” that a skilled artisan would understand “that it equates to an explicit one.” Thorner, 669 F.3d at 1368 (citation modified). “Simply referring to two terms as alternatives or disclosing embodiments that all use the term[s] the same way is not sufficient to redefine a claim term.” Id. But “when a patent repeatedly and consistently characterizes a claim term in a particular way, it is proper to construe the claim term in accordance with that characterization.” GPNE Corp. v. Apple Inc., 830 F.3d 1365, 1370 (Fed. Cir. 2016) (citation modified).

In Aortic Innovations LLC v. Edwards Lifesciences Corp., No. 2024-1145, __ F.4th __ (Fed. Cir. Oct. 27, 2025), the patents-in-suit disclosed dual-frame configurations for a transcatheter aortic valve replacement device having an “outer frame” and an “inner frame” working together. The issue was whether the patent's specification implicitly redefined “outer frame” as a self-expanding frame. 

     A patent's consistent and clear interchangeable use of two terms can result in a definition equating the two terms. See Edwards Lifesciences LLC v. Cook Inc., 582 F.3d 1322, 1329 (Fed. Cir. 2009); Wasica Fin. GmbH v. Cont'l Auto. Sys., Inc., 853 F.3d 1272, 1282 n.6 (Fed. Cir. 2017) (highlighting interchangeable use within the claims and within the written description); Bid for Position, LLC v. AOL, LLC, 601 F.3d 1311, 1317–18 (Fed. Cir. 2010) (highlighting interchangeable use within a claim and within certain embodiments); Bell Atl., 262 F.3d at 1274–75 (highlighting interchangeable use within the written description and within the prosecution history); Tate Access Floors, Inc. v. Maxcess Techs., Inc., 222 F.3d 958, 968 (Fed. Cir. 2000) (highlighting interchangeable use throughout the abstract and summary of invention).

     For example, in Edwards, the “specification consistently use[d] the words ‘graft' and ‘intraluminal graft' interchangeably.” Edwards, 582 F.3d at 1329. Specifically, the court noted the interchangeable use of the claimed term “graft” and the narrowed term “intraluminal graft” in the disclosure of the invention of U.S. Patent 6,582,458 at 1:57–59 and in the “preferred embodiment” at columns 5 and 6. Id. The court then concluded that the interchangeable use of the two terms was “akin to a definition equating the two.” Id. 

     Here, a skilled artisan would understand that the claimed term “outer frame” is a “self-expanding frame.” First, when discussing structure 416 in the dual-frame transcatheter valve embodiment and structure 216 in the dual-frame endograft device embodiment, the specification refers to these structures as an “outer frame,” a “self-expanding frame,” and a “self-expanding outer frame” several times. 

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     Second, beyond the discussion of structures 416 and 216, the specification consistently indicates that claim 1's “outer frame” is a “self-expanding frame.” ... [The specification] says that “[t]he transcatheter valve includes a frame component having a balloon-expandable frame . . . and a self-expanding frame secured to the balloon expandable frame.” J.A. 174, 3:62–65. In the paragraphs immediately following this statement, the specification notes that “[i]n some embodiments,” other features may be present, but it never limits the presence of a self-expanding frame to only “some embodiments.” See J.A. 174, 4:5–35. The contrast in the language indicates that a transcatheter valve must have a self-expanding frame and a balloon-expanding frame, whether it be configured as a serial-frame or a dual-frame.

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     In sum, a skilled artisan, when reading the patent, would understand that the “very character of the invention [of a transcatheter valve] requires the [self-expanding] limitation be a part of every embodiment.” Alloc, Inc. v. Int'l Trade Comm'n, 342 F.3d 1361, 1370 (Fed. Cir. 2003).

Professor Crouch noted that “[a]lthough the Federal Circuit describes this [implicit lexicography] standard as quite strict (requiring a definition ‘so clear' that it equals an explicit one), the Aortic court illustrates how that threshold can be satisfied quite easily in practice.”