the manufacture and/or use of an invention or improvement for which someone else owns a patent issued by the government, without obtaining permission of the owner of the patent by contract, license or waiver.
Under the Patents Act 1977, where the patented invention is a product, it is infringed if the infringer, without the patentee's permission, makes, disposes of, offers to dispose of, uses or commercialises products embodying the invention in the UK. As to processes, infringement includes using the process or offering the process for use. It is also (secondary) infringement to knowingly supply or offer information related to an essential element of the invention to others. Exceptions to infringement include where the law considers that an implied licence has been granted, exhaustion of rights or non-commercial use. In addition the defendant may claim the infringement was innocent - viz he was unaware and should not reasonably have been aware that he was infringing the holder's rights. In this instance the plaintiff may be unable to claim compensation for the breach.
A patent provides the proprietor of that patent with the right to exclude others from utilizing the invention claimed in that patent. Should a person utilize that invention, without the permission of the patent proprietor, they may infringe that patent.