While I am sure he gave many memorable speeches, Bill Clinton’s most famous statement as president may actually be the following: “It depends upon what the meaning of the word ‘is’ is.” This, of course, was Clinton’s response in 1998 when asked to elaborate upon former statements he had made about illicit sexual encounters with female assistant Monica Lewinsky. However strong of an argument this may have been in avoiding impeachment as president, it does highlight the importance of the meaning of even the smallest of words.

What does this have to do with patent law? Well, a lot actually. I have often written of how important it is to carefully craft a patent application and to be cognizant of the words selected to describe an invention. When millions of dollars are at stake, even the meaning of the smallest words can become contentious. While Bill Clinton debated the meaning of the word “is,” a court in the United States has opined on the meaning of the word “a” during patent litigation.

Once a patent is granted by a patent office, the inventor is provided with a right to exclude others from making, using or selling the claimed invention. If the inventor suspects that someone is infringing the patent, he or she must prove that the allegedly infringing product falls within the claims of the issued patent.

Let me provide you with an example of how the meaning of a simple word in a patent claim can become very contentious during an infringement action. In everyday life, we generally understand what the word “thin” means. We may not be able to give the word a precise definition, but we know it when we see it. A piece of paper is thin. Saran Wrap is thin. However, what does “thin” mean in the following hypothetical patent claim: “A packaging material comprising a substrate and a thin film of polyethylene.” If you were being sued for a million dollars for infringement of this claim, one argument you would likely advance is that the film of polyethylene on your packaging material is not “thin.” Patents are therefore usually drafted with more definitive language. Subjective words create ambiguity in patents and for this reason you won’t often see such words in a patent claim. In this instance, such ambiguity in the claim could be avoided by numerically defining the meaning of the term. However, numerically defining such a term in a broad claim can also be problematic for an inventor. For example, if the term “thin” was defined in this patent claim to mean between one and two millimetres, one could possibly avoid infringement by using a thickness of three millimetres, assuming the invention still operates at such a thickness.

In reality, any word or term in a patent claim can become contentious during patent litigation, where each party advances a definition for the term that supports their position. Before deciding on issues of infringement, a judge must construe the meaning of any terms in a patent claim that could have a bearing on the outcome of the infringement action. In legalese, this exercise is called claim construction. While it may seem straightforward to define words or terms, claim construction is often a complex exercise, which takes much time and photo by jess ica deeks With patents, the devil is always in the details usually involves expert witnesses. In a recent Canadian case involving polyethylene polymers, the judge had to construe the following terms: “ethylene polymer composition,” “comprising,” “homogenously branched,” “heterogeneously branched,” “linear,” “substantially linear,” “slope of strain hardening coefficient” and “linear polymer fraction.” While such terms may be well known to polymer chemists, these are not your average everyday phrases. The judge in this case needed to provide meaning to each of these terms, taking into account opposing arguments from each side in the litigation. In the end, when describing an invention, it’s important to use clear language that accurately defines the invention but which still provides the inventor with broad enough protection so that the patent is valuable.