Tiny Word ‘About’ Speaks Volumes of Patent Drafting Tightrope

One of the simplest words in the English language became the focus of a recent federal appeals court ruling highlighting a fundamental challenge in patent law: how much space a claim can cover before its boundaries become unclear.

The US Court of Appeals for the Federal Circuit last month invalidated claims from Enviro Tech Chemical Services Inc.’s US Patent No. 10,912,321 because the patent’s use of “about” to describe a claimed pH range failed to clearly define the claims’ scope.

The opinion didn’t eliminate drafting tools like “about.” But legal observers say it’s a prime example of how the same flexibility that can make patent claims more valuable can also leave them vulnerable when the public can’t tell where the claimed territory ends.

Patent claims define the legal boundaries of an invention, much like property lines define the boundaries of a piece of land. But unlike a fence or survey marker, patent claims are expressed in words—making precision critical because competitors and the public need to know what falls inside or outside the patent’s boundaries.

The Federal Circuit found the uncertainty surrounding “about” made Enviro Tech’s claims indefinite—a patent-law term meaning the company failed to clearly inform the public what the patent covered and what remained available to others.

Patent prosecutors who shepherd inventions through the patent-application process often use words like “about,” “approximately,” and “substantially” to avoid locking claims to rigid numerical boundaries. But that added breadth can undermine a patent when the record doesn’t explain its limits—especially when the claimed invention sits close to what already existed.

A rigid cutoff can give competitors room to make minor changes while capturing the benefit of a patented invention, said David B. Gornish, a former patent litigator who now focuses primarily on patent preparation and prosecution at Eckert Seamans.

“We don’t want to give someone an easy out to just be 0.1 on the other side of our claim range and get the same results,” he said. “And so that’s why we would use terms of degree.”

Terms of Degree

The problem in the Enviro Tech case wasn’t the word “about” itself, which “is one of the most common words in patent claims,” said Dennis Crouch, a law professor at the University of Missouri who runs the Patently-O blog.

Courts have allowed this and similar approximation language in patent claims for more than a century, as long as the public can determine just how much flexibility those words provide.

Enviro Tech’s ‘321 patent covered methods of treating poultry with a type of antimicrobial water adjusted within a claimed acidity range—a pH level “of about 7.6 to about 10.”

The Federal Circuit said neither the patent’s specification, which describes the invention, nor its prosecution history—the record of the back-and-forth with the US Patent and Trademark Office before a patent is granted—provided enough guidance on how far the claimed pH range extended.

That became especially important because the prior art already involved a pH level close to the ‘321 patent’s claimed boundary. Prior art helps define what was already known before an invention and thus the limits of what a subsequent patent can claim.

“At no point in the entire prosecution history does Enviro Tech explain what ‘about’ means,” the court said. Enviro Tech, it added, “never offered an argument to the examiner indicating what ‘about’ means.”

At the same time, patent prosecutors must avoid reaching so broadly that their claims overlap with earlier inventions, Gornish said.

“We want to be as precise as we can be, and trying to do justice to the invention, for the client, to get as reasonably broad as we can get without putting our foot into the territory of the prior art,” he said.

The back-and-forth with the PTO can shape a patent’s meaning years later, making consistency in those communications critical, Gornish said. The words of an issued patent claim tell only part of the story because statements made while securing approval can affect its value later, he said.

“It’s kind of like in Miranda warnings in criminal procedure—anything you say can and will be used against you,” he said. “There always has to be this mindfulness of making sure that the story hangs together.”

Inherent Tension

Debbie McComas, a lawyer for Haynes & Boone LLP who argued for Safe Foods Corp. in its Federal Circuit win against Enviro Tech, said she recognizes “the tension that patent prosecutors face in drafting a specification that captures the broadest invention possible while acknowledging the scope of what came before.”

But flexible terms like “about” need clearer limits when claims approach existing technology, she said.

“The prior art was helpful in reinforcing the need for such clarity because it left little to no room to distinguish the claimed invention from what already existed,” McComas said.

David Sanker, a patent attorney and founder of SankerIP, doesn’t see patent drafters changing their behavior despite the risk.

Few patents end up in litigation, and “broad, vague language” can provide leverage in licensing discussions, he said.

Yet Gornish warned that even small drafting choices can carry major consequences.

“Words are powerful,” he said. “We want to be very precise in the words that we choose to express what we want to say. Sometimes, when we’re not precise, when we’re not really saying what we’re trying to say, or we’re not saying it clearly enough, we can run into trouble.”