“I meant what I said and I said what I meant. An elephant’s faithful one-hundred percent!”   ― Dr. Seuss, Horton Hatches the Egg

With elephants, at least according to Dr. Seuss, it’s all relatively straight forward.   But when it comes to patent claims, do they say what the mean and mean what they say?

 Patent claim interpretation is generally a task undertaken by a patent attorney or at least, with one by your side.  However, you may want a quick peak behind the curtain to understand why this is so.  As part of an R&D team, a founder, CTO or CSO, you may find yourself looking at patent claims and wondering if they cover the product or process you are currently developing.

At first, it may seem simple, the claims are a product with a list of features or a method with a number of steps. Are the words of the claims limited to what you think they mean?  The patent world is a different story from Horton the elephant.  Context matters, and in some cases, the context can shape the meaning of terms in a manner unanticipated by just looking at the words of the claim.


When analyzing whether a product or process infringes a patent claim, the first step in the analysis is claim construction, identifying the meaning and scope of the claim terms.  In the US, when infringement becomes an issue, it is addressed in the federal court system.  The summary below describes some of the primary rules that shape the analysis.

Plain and ordinary meaning

Claim terms are interpreted by looking to their “plain and ordinary meaning as understood by a person of ordinary skill in the art.”[1]  Basically, the court looks at how someone working in the same scientific field at the time the patent was filed would define the term.

This approach has 2 important parts.  First, it isn’t the person on the street view or a lawyer’s definition of a term, but ostensibly a scientist or engineer or whatever is appropriate to the subject matter of the claim.  Second, the claim term is defined in the appropriate time frame, which is the effective filing date of the patent.  This can be meaningful, as terms may evolve as the field advances.  For example, in one case, the term “copolymer of lactic acid and glycolic acid” was held to be synonymous with “copolymer of lactide and glycolide” because at the time the patent was filed “the language was relatively loose at that point in time with respect to the use of those terms.”[2]

Patentee as a lexicographer

There are some instances when the plain and ordinary meaning does not govern.  For example, a patentee can define a term in the patent and give it something other than its plain and ordinary meaning.[3]   In some instances, a patentee will coin a new term and the only definition that exists is how the term is defined or used in the patent.  In other cases, the patentee can use a known term in a manner the runs contrary to its common meaning.  For example, in Allergan v. Barr Labs., the court determined that although -N(R4)2 would normally mean two identical R4 groups, Allergan had defined it in the patent by including 2 non-identical R4 groups as part of its claimed pharmaceutical compounds.[4] The meaning provided in the patent therefore governed the infringement analysis.

It’s all in the context

When looking at how a term would be viewed by someone in the same field, context comes into play.  This context is the use of the term in the specification (body) of the patent, and also in the prosecution history (the back-and-forth between the patentee and the United States Patent & Trademark Office (USPTO) from the time when the application is submitted to the grant of the claims in their final form). [5] Relevant extrinsic evidence, like scientific publications and opinions from experts in the field, can also be considered.  However, these external sources get less weight than the specification and prosecution history.

There is a balance.  While the use of the term in the patent is often considered “the single best guide” to the term’s meaning, there is a backstop which prevents importing certain limitations into the claim language.[6]  For instance, simply because a patent provides only a single example or a preferred embodiment, this does not necessarily mean that the term is limited to that one disclosure.  For example, in a case concerning a method for measuring glucose concentration in blood, the claim term at issue was “upon detection of a suitable stable endpoint.” The patent provided an example that used a predetermined time for the reaction.  However, the claims were interpreted much broader because the patentee had not explicitly disavowed using methods without a predetermined reaction time, and the context of the patent specification overall indicated that one would interpret the term in its broader sense.

On the flip side, the patent can contain “repeated and definitive remarks” which disclaim a broader meaning and limit the term’s scope.[7]  For instance, where a patent stated “Cell lines grown as a monolayer or on beads, as opposed to cells grown in three-dimensions, lack the cell-cell and cell-matrix interactions characteristic of whole tissue in vivo,” as one of several distinctions made between the types of culture methods, it confined the meaning of “bead” to exclude 3-dimensional cell culture.[8]

A few more things just to keep your head spinning

Claims can be broader than their literal meaning

While not part of what is termed “claim construction,” the doctrine of equivalents (DOE) can come into play in deciding whether or not your product or service infringes a patent claim.  Under DOE, a product or service may infringe even if it doesn’t meet the literal language, if it “performs substantially the same function in substantially the same way to obtain the same result as the claim limitation.”[9]

Layered on top of this equivalency test is the consideration of whether DOE is available for the patent claim of interest.  If the patentee surrenders certain claim coverage during prosecution, either by a clear surrender of material in arguments made to the USPTO or by narrowing the claims to overcome patentability rejections, then the patentee cannot recapture this lost territory using DOE.[10]

Where you are matters

In the US, patents get interpreted by two different adjudicative pathways.  When questions of infringement are at play, the patent questions are addressed in the federal court system.  During the period when patents are being prosecuted and in post-grant proceedings challenging validity, examiners at the USPTO and the Patent Trial and Appeal Board (PTAB), respectively, handle the issues.  These 2 pathways do not adhere to the same set of rules, although there is some overlap.

One of the most noticeable differences is the application by the USPTO and PTAB of the “broadest reasonable interpretation” (BRI) to claim terms, rather than the plain and ordinary meaning.  The BRI is shaped by the patent specification, but tends to be broader than the standard applied in federal court.  A justification for the broader standard is to guard against overly broad claims by encouraging applicants to draft and amend claims to a narrower scope.[11]  Thus, claim scope may differ depending on whether you are looking at claims with an eye towards enforcement in court or as challenged in a post-grant proceeding such as an inter partes review (IPR).


  • Interpreting claims is context-specific
  • Claims are shaped by their literal language, the patent specification and the prosecution history
  • Usage of terms by those in the relevant scientific field at the time the patent was filed can provide context
  • For purposes of an infringement analysis, claim scope may be broader than the literal terminology using DOE
  • Claims may be interpreted differently in a court proceeding (as compared with post-grant proceedings like inter partes review (IPR)



This blog and its take-aways are not legal advice and should not be construed to be legal advice.  Issues of claim interpretation are circumstance and fact-specific.  You should consult an attorney in your jurisdiction for guidance on your particular situation.

[1] Phillips v. AWH Corp., 415 F.3d 1303, 1313 (Fed.Cir.2005) (en banc).

[2] Tap Pharm. Prod., Inc. v. Owl Pharm., 419 F.3d 1346, 1349–50 (Fed. Cir. 2005).

[3] Thorner v. Sony Comput. Entm’t Am., 669 F.3d 1362, 1365 (Fed. Cir. 2012).

[4] Allergan, Inc. v. Barr Labs., 501 F. App’x 965, 969 (Fed. Cir. 2013).

[5] Phillips, 415 F.3d at 1313-17.

[6] Phillips, 415 F.3d at 1315, 1323.

[7] SkinMedica, v. Histogen, 727 F.3d 1187, 1196 (Fed. Cir. 2013).

[8] SkinMedica, 727 F.3d at 1197.

[9] Pozen v. Par Pharm., 696 F.3d 1151, 1167 (Fed.Cir.2012).

[10] Spectrum Pharm. v. Sandoz, 802 F.3d 1326, 1337 (Fed. Cir. 2015).

[11] Cuozzo Speed Techs. v. Lee, 136 S. Ct. 2131, 2145, (2016).