Patent holders have certain exclusive rights, namely the exclusive right to manufacture, use, sell, and import the patented invention. Patent infringement is when these exclusive rights are violated. The unauthorized manufacture, use, sale, or importation of a patented invention without the holder's permission is patent infringement.

For example:

• Unauthorized manufacture: In 2011, Apple sued Samsung for "slavishly copying the iPhone's design and software features” (Kaya 2018) and integrating them into their Galaxy phones to sell.

• Unauthorized use: This would be if Company A has a patented method to develop a certain product glass. And Company B uses that method to create its glass without Company A’s permission.

• Unauthorized sale: If Company B sells phones with a patented screen technology owned by Company A without authorization.

• Unauthorized Importation: If Company A holds a patent for a new type of ticking for a watch, and Company B imports and sells watches that use this technology without obtaining a license or permission.

There are two general types of infringement. First, literal infringement, which is when the accused product contains a replica of at least one claim of the patented invention since it contains every element of that claim. Second, the doctrine of equivalents, which occurs when the allegedly infringing item is substantially similar. In this situation, the infringing product achieves the same goal as the patented product by performing essentially the same function in the same way.

There are three main defenses that can be used to argue against allegations of patent infringement. Firstly, the accused party may prove that their process, product, or composition does not infringe the patent in question, either literally or under the doctrine of equivalents. Secondly, the accused party may prove that the patent in question is invalid. It's important to note that just because the USPTO issued a patent does not necessarily mean that the patent is valid. If the patent is found to lack novelty, nonobvious, or not meet any other legal requirements for patents, it may be deemed invalid. And lastly, the Prior Use Defense which is “A prior user right is the right of a third party to continue the use of an invention where that use began before a patent application was filed for the same invention.” (USPTO).