Every Word Will Be Attacked: What Founders Need to Know About Patent Language

Why It Matters

Indefiniteness can wipe out a patent portfolio, leaving companies vulnerable to competitors and costly litigation. The ruling forces startups to prioritize clear, numeric claim language over broad, ambiguous wording.

Key Takeaways

• “About” appeared 241 times in the patent, never defined.
• Federal Circuit invalidated all 27 asserted claims for indefiniteness.
• Inconsistent experimental data amplified the indefiniteness argument.
• Silence in prosecution history triggered estoppel, blocking equivalents.
• Founders must define relative terms with numeric limits or examples.

Pulse Analysis

The Federal Circuit’s 2026 decision against Enviro Tech underscores a core principle of patent law: a claim must convey a clear, bounded invention. Courts apply the indefiniteness standard when a term—such as “about,” “approximately,” or “substantially”—lacks a concrete definition in the specification or prosecution record. In Enviro Tech’s case, the repeated use of “about 7.6 to about 10” without numeric limits left the claim’s scope ambiguous, allowing the challenger to argue that the patent could not reliably delineate its coverage. This outcome demonstrates that even robust experimental data cannot rescue a claim that fails the clarity test.

For founders and early‑stage companies, the lesson is pragmatic: draft claims as if they were contracts read by opposing counsel, not merely by examiners. Every relative term should be anchored by explicit ranges, examples, or functional descriptions that are consistent across the specification. During prosecution, any amendment that narrows a claim must be accompanied by a clear explanation; silence can later be interpreted as an admission of indefiniteness and may trigger prosecution‑history estoppel, eliminating the doctrine of equivalents as a fallback. A disciplined review checklist—spotting words like “about,” “approximately,” “fast,” or “high‑quality,” and demanding precise definitions—can prevent costly invalidations.

The broader industry impact is a shift toward defensive patent drafting. Companies are increasingly using continuations and continuation‑in‑part applications to refine language before issuance, treating each filing as a second chance to tighten ambiguous terms. This proactive approach not only safeguards existing IP but also strengthens enforcement positions when disputes arise. As the Enviro Tech case shows, vague language is a liability; precise, well‑supported claim language is a strategic asset that can preserve market advantage and investor confidence.