A patent grants the right to exclude others from using, offering for sale, selling, importing or manufacturing the claimed invention in the United States.
Every patent shall contain a short title of the invention and a grant to the patentee, his heirs or assigns, of the right to exclude others from making, using, offering for sale, or selling the invention throughout the United States or importing the invention into the United States.
— 35 U.S. Code §154.
A patent holder may recover monetary damages when their right to exclude is unlawfully violated. Such a violation is called patent infringement–the party responsible for this unlawful violation is called an infringer and is said to infringe the valid patent.
patent holder, and the holder's lawful licensees, can recover for monetary injury when their exclusive rights are violated by others' wrongful conduct. One form of patent injury occurs if unauthorized persons or entities copy, use, or otherwise infringe upon the patented invention. Another form of injury to the patent holder or his licensees can occur when the actor induces others to infringe the patent.
— Commil USA, LLC v. Cisco Systems, Inc., 135 S. Ct. 1920, 1923– 24 (S. Ct. 2015).
There are at least three ways infringement can occur including directly, through inducement, or through contributory infringement. I discuss each form of infringement in this chapter.