How is a patent claim construed in court? On this there is wide disagreement among the judges who decide such legal questions. 

The U.S. Supreme Court in June approved the PTAB using "broadest reasonable interpretation" rather than "plain meaning" patent claim construction, but without explaining either methodology.1 This was a missed opportunity to resolve the Federal Circuit's sharp internal divide over "plain meaning" patent claim construction. All panels cite, of course, the 11-year old governing en bane Phillips decision on patent- claim construction methodology.2 But, there the agreement ends as panels diverge on how to determine "plain meaning" and how that relates to the correct legal construction of a patent claim.

Below are four basic questions about "plain meaning" construction on which the Federal Circuit is divided or the Federal Circuit appears to have diverged from the Supreme Court. These are not trivial, academic disagreements. How a particular panel answers these four questions often will dictate how it will decide a patent-claim construction dispute on appeal.3

1. Does “plain meaning” claim construction always require an effort to determine the contextual meaning of the claim language in view of the specification? 


  • "The terms at issue have so clear an ordinary meaning that a skilled artisan would not be looking for clarification in the specification."4 
  • "In construing a claim term, we look to the words of the claim itself. If the claim term has a plain and ordinary meaning, our inquiry ends. If, however, the claim term does not have an ordinary meaning, and its meaning is not clear from a plain reading of the claim, 'we turn to the remaining intrinsic evidence, including the written description, to aid in our construction of that term.''" 
  • "The district court could have ended its analysis with the plain language [of the claims]."6 


  • "The only meaning that matters in claim construction is the meaning in the context of the patent."7 

2. Does “plain meaning” claim construction presume that the acontextual ordinary meaning of claim language is the correct construction, overcome only by a clear redefinition or clear disclaimer in the intrinsic evidence?  


  • "[A] claim term is only given a special definition different from the term's plain and ordinary meaning if the 'patentee ... clearly set[s] forth a definition of the disputed claim term other than its plain and ordinary meaning.' A patentee can also disavow claim scope, but the standard 'is similarly exacting.'"8 
  • ''We depart from the plain and ordinary meaning of claim terms based on the specification in only two instances: lexicography and disavowal. The standards for finding lexicography and disavowal are exacting."? 


  • A court must apply to patent claims "the standard construction rule that a term can be defined only in a way that comports with the instrument as a whole."!" And, courts must seek that construction which "fully comports with the specification and claims and so will preserve the patent's internal coherence.'?' 

3. Under “plain meaning” claim construction, is the scope of a patent claim presumptively limited by the scope of the disclosed invention? 


  • "It is not for the court to tailor the claim language to the invention disclosed."12 


  • "[With the trial court's broader construction] the patent would claim more than the patentee actually invented."!" 
  • "Therefore, in construing a claim there are two limiting factors-what was invented, and what exactly was claimed. To determine the former-what was invented-we look at the entire patent, with particular attention to the specification (the written description of the invention and the several claims  made). To determine the latter-what exactly was claimed-the focus is on the precise words of the particular claim or claims at issue; the written description and preferred embodiments are aids in understanding those words."!" 
  • "In reviewing the intrinsic record to construe the claims, we strive to capture the scope of the actual invention, rather than strictly limit the scope of claims to disclosed embodiments or allow the claim language to become divorced from what the specification conveys is the invention."15 

4. Under “plain meaning” claim construction, are claim amendments strictly construed against the patent owner? 


  • ''When the prosecution history is used solely to support a conclusion of patentee disclaimer, the standard for justifying the conclusion is a high one. '[F]or prosecution disclaimer to attach, our precedent requires that the alleged disavowing actions or statements made during prosecution be both clear and unmistakable.' Where the alleged disavowal is ambiguous, or even 'amenable to multiple reasonable interpretations,'we have declined to find prosecution disclaimer ."16 


  • A claim amendment during prosecution of a patent "operates as a disclaimer" and "must be strictly construed against [the applicant]" and in favor of the public.'? By  substituting one phrase for another to overcome a rejection of a proposed patent claim, the patent applicant "recognize[s] and emphasize[s] the difference between  the two phrases and proclaim[s] his abandonment of all that is embraced in that difference."18 
  • "'Limitations imposed by the inventor, especially such as were introduced into an application after it had been persistently rejected, must be strictly construed  against the inventor and in favor of the public, and looked upon as in the nature of disclaimers."'19 

In trial court actions and on appeal, litigants may wish to look for and preserve opportunities to seek en bane review of these questions. For example, patent challengers may wish to preserve the following positions: 

First, there is no presumption favoring the acontextual meaning of patent claim language which the specification and prosecution history can overcome only with clear redefinitions or clear disavowals. Instead, the scope of a patent claim is limited by the  claim language as understood by a skilled artisan at the time of the alleged invention and in the context of the specification and prosecution history. In other words, courts must consider the intrinsic evidence before deciding "plain meaning," not after. 

Second, the scope of a patent claim also is limited, presumptively, by the scope of the patent's disclosed invention, not only by the contextual meaning of the claim language. Sometimes, of course, a claim cannot fairly be construed as narrowly as the disclosed invention, raising a written description or enablement invalidity defense. But, nevertheless, when construing a patent claim a court should bear in mind that patent claims presumptively satisfy the statutory mandates that an applicant claim only that invention which the applicant regards as the invention and discloses in the specification. 20 

Third, narrowing amendments of a patent claim in the Patent Office are strictly construed against the patent owner.