Guides · Patent Litigation
Patent Basics for Litigation, with a Glossary
A patent is a right to stop others from making, using, selling, offering, or importing a claimed invention.
· Law checked through October 20, 2026
In Short
A patent is a right to stop others from making, using, selling, offering, or importing a claimed invention. It is not a right to use the invention. Litigation turns on the patent's claims, its term, and who owns it. The glossary at the end defines the terms used throughout this section.
Common situations.
- A business receives a letter citing a patent number and wants to know what the patent actually covers.
- A company buys a patent and wants to know whether it can sue.
- A licensee wonders whether it can enforce the licensed patent on its own.
- Two companies dispute who owns a patent developed under a joint project.
What a patent gives its owner.
A patent gives its owner the right to exclude others from making, using, offering for sale, selling, or importing the invention in the United States (35 U.S.C. § 154(a)(1)). Anyone who does those things without authority infringes (§ 271(a)). The patent does not give its owner permission to use the invention; another patent may cover part of the same product.
How long a patent lasts.
- Utility patents generally end 20 years after the earliest nonprovisional application was filed (§ 154(a)(2)). The term can be extended to make up for Patent Office delay (§ 154(b)). A provisional application does not start the 20-year clock.
- Design patents issued from applications filed on or after May 13, 2015 last 15 years from grant (§ 173).
- Plant patents follow the utility rules (§ 161).
- Maintenance fees. A utility patent lapses if a maintenance fee due 3½, 7½, or 11½ years after grant goes unpaid after the grace period (§ 41(b)).
An expired patent can still support a suit for past infringement, within the six-year limit on damages (§ 286).
What is inside a patent.
- The specification describes the invention and how to make and use it (§ 112(a)).
- The drawings illustrate it.
- The claims, the numbered sentences at the end, define what the patent covers (§ 112(b)). An independent claim stands alone. A dependent claim refers to an earlier claim and adds limits (§ 112(d)). Each claim is a separate right: one may be infringed or invalid while another is not.
The claims work like a property deed's boundary description. A product infringes only if it falls within at least one claim.
How a patent is obtained.
An inventor files an application with the U.S. Patent and Trademark Office, and an examiner compares the claims with earlier patents and publications. The written record of that exchange, called the prosecution history or file history, matters in litigation: statements made to win the patent can narrow what the claims cover. See The Patent Application Process at the USPTO.
What can be patented.
A patent may cover a process, machine, manufacture, or composition of matter, or an improvement of one (§ 101). Laws of nature, natural phenomena, and abstract ideas cannot be patented as such. Courts apply a two-step test: is the claim directed to one of those exceptions, and if so, does it add an inventive concept that makes it more than the exception itself (Alice Corp. v. CLS Bank Int'l, 573 U.S. 208 (2014); Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66 (2012)). In 2025 the Federal Circuit held that claims applying generic machine learning to a new data environment are not patent-eligible (Recentive Analytics, Inc. v. Fox Corp., No. 2023-2437 (Fed. Cir. Apr. 18, 2025), cert. denied (Dec. 8, 2025)).
Who can sue.
- The patentee, including successors in title (35 U.S.C. §§ 100(d), 281).
- An exclusive licensee that holds all substantial rights may sue in its own name. A licensee with lesser rights generally must join the patent owner (Lone Star Silicon Innovations LLC v. Nanya Tech. Corp., 925 F.3d 1225 (Fed. Cir. 2019)).
- Co-owners. All co-owners must ordinarily join as plaintiffs, and one co-owner cannot be forced to join (STC.UNM v. Intel Corp., 754 F.3d 940 (Fed. Cir. 2014)). Each co-owner may use and license the patent without the others' consent (§ 262).
- Recording assignments. An assignment not recorded at the Patent Office within three months can be void against a later buyer who paid value without notice (§ 261). Check the Assignment Center before assuming who owns a patent.
A dispute over who owns a patent, under an employment agreement or a sale contract, usually turns on state contract law and can be heard in Texas state court.
Who gets sued.
Manufacturers, importers, distributors, retailers, and customers can all infringe by making, using, or selling. Many disputes involve a chain: the patent owner sues a customer, the customer looks to its supplier, and the supplier looks to its contract and the Texas UCC warranty against infringement (Tex. Bus. & Com. Code § 2.312(c)).
Glossary.
| Term | Meaning |
|---|---|
| Abstract idea | A concept that cannot be patented by itself; see § 101 and Alice. |
| ANDA | Abbreviated New Drug Application; filing one to sell a generic drug before a patent expires is itself infringement (§ 271(e)(2)). |
| Anticipation | Invalidity because a single earlier reference discloses every element of a claim (§ 102). |
| Apportionment | Limiting damages to the value of the patented feature, not the whole product. |
| Assignment | A transfer of ownership of a patent. |
| Claim | A numbered sentence defining what the patent covers. |
| Claim chart | A table comparing each element of a claim with a product or a prior-art reference. |
| Claim construction | The court's ruling on what disputed claim terms mean; also called a Markman ruling. |
| Contributory infringement | Supplying a component especially made for an infringing use, with no substantial noninfringing use (§ 271(c)). |
| Declaratory judgment | A lawsuit by an accused party asking a court to declare that it does not infringe or that the patent is invalid. |
| Dependent claim | A claim that incorporates an earlier claim and adds limits. |
| Design patent | A patent on the ornamental design of a manufactured article. |
| Direct infringement | Making, using, offering, selling, or importing the claimed invention without authority (§ 271(a)). |
| Doctrine of equivalents | Infringement by a product that differs from a claim only insubstantially. |
| Element (limitation) | One requirement of a claim; a product must meet every one. |
| Enhanced damages | Damages increased up to three times for egregious infringement (§ 284). |
| Exceptional case | A case in which the court may award attorney's fees to the winner (§ 285). |
| Exclusion order | An ITC order barring infringing imports. |
| Ex parte reexamination | A Patent Office review of a patent's claims in light of earlier patents and publications, in which the requester does not take part after filing. |
| File history | The record of the application's examination; also called the prosecution history. |
| Indefiniteness | Invalidity because a claim does not tell skilled readers its scope with reasonable certainty (§ 112(b)). |
| Induced infringement | Actively encouraging another's direct infringement, knowing it infringes (§ 271(b)). |
| Inequitable conduct | Deceiving the Patent Office during examination; it makes the whole patent unenforceable. |
| Inter partes review (IPR) | A trial at the Patent Trial and Appeal Board to cancel claims as anticipated or obvious over earlier patents and publications. |
| ITC | The U.S. International Trade Commission, which can exclude infringing imports under Section 337. |
| Lost profits | Damages measured by sales the patent owner would have made but for the infringement. |
| Marking | Labeling a patented product with its patent number; failure to mark can limit damages (§ 287). |
| Nonpracticing entity | A patent owner that licenses or enforces patents rather than making products. |
| Obviousness | Invalidity because the invention would have been obvious to a person of ordinary skill in light of earlier work (§ 103). |
| Person of ordinary skill in the art | The hypothetical skilled worker from whose view claims are read and obviousness is judged. |
| Post-grant review (PGR) | A PTAB trial on any ground of invalidity, available only within nine months after grant. |
| Prior art | Earlier patents, publications, sales, and public uses against which a claim's novelty and obviousness are judged. |
| PTAB | The Patent Trial and Appeal Board of the Patent Office. |
| Reasonable royalty | Damages measured by the royalty the parties would have agreed to just before infringement began. |
| Specification | The written description of the invention. |
| Willful infringement | Deliberate or egregious infringement that can support enhanced damages. |
Sources.
- 35 U.S.C. §§ 41(b), 100, 101, 112, 154, 161, 173, 261, 262, 271, 281, 284, 285, 286, 287.
- Tex. Bus. & Com. Code § 2.312(c).
- Alice Corp. v. CLS Bank Int'l, 573 U.S. 208 (2014).
- Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66 (2012).
- Recentive Analytics, Inc. v. Fox Corp., No. 2023-2437 (Fed. Cir. Apr. 18, 2025), cert. denied, No. 25-505 (U.S. Dec. 8, 2025).
- Lone Star Silicon Innovations LLC v. Nanya Tech. Corp., 925 F.3d 1225 (Fed. Cir. 2019).
- STC.UNM v. Intel Corp., 754 F.3d 940 (Fed. Cir. 2014).
- USPTO Assignment Center.
This guide is general information, not legal advice. Law checked through October 20, 2026. See the Disclaimer.