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Doctrine of equivalents

Definition

A legal doctrine that extends patent protection beyond the literal scope of the claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →. Even if a competitor's product doesn't literally include every element of a claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more →, infringementinfringementMaking, using, selling, or importing a patented invention without permission from the patent holder.Read more → may still exist if each claim element is performed by a substantially similar function in a substantially similar way. Courts apply this doctrine to prevent competitors from making trivial changes to avoid literal infringement.

Related terms

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Dependent claim

A claim that refers back to and further limits another claim. For example: "The device of claim 1, wherein the housing is made of aluminum." If the claim it depends on is invalid, the dependent claim also falls. Dependent claims provide narrower protection but serve as fallbacks — if broader independent claims are invalidated, narrower dependent claims may survive.

Design patent

A patent covering the ornamental appearance of a functional object — its shape, configuration, or visual design — not how it works. Design patents last 15 years from grant. They are faster and less expensive to obtain than utility patents. Apple's US D618,677 patent on the iPhone's rounded-rectangle shape is a famous example; it was central to over $1 billion in damages against Samsung.

Divisional

A patent application split off from a parent application because the USPTO determined the parent contained claims to more than one distinct invention. When an examiner issues a "restriction requirement," the applicant must elect one group of claims to pursue in the parent; the rest can be filed as a divisional. Divisionals get the parent's original filing date.

Abstract

A brief summary (300 words or fewer) that appears at the top of every patent. The abstract describes what the invention does in general terms. Legally, it has almost no weight — courts use the claims to determine what a patent covers, not the abstract. The abstract is useful mainly for quickly scanning patents during a prior art search.

Anticipation

A legal standard for rejecting a patent claim. If every element of a claim was already disclosed in a single prior art reference — in a patent, article, or product — the claim is "anticipated" and cannot be patented. Anticipation requires a single source to contain every element; if you need two sources, it's an obviousness argument, not anticipation.

Appeal

A request to have a patent examiner's rejection reviewed by a higher authority. After receiving multiple rejections, an applicant can appeal to the Patent Trial and Appeal Board (PTAB) within the USPTO, and from there to federal court. Appeals are expensive and slow, but sometimes necessary when an examiner applies the law incorrectly.

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