Novelty is a requirement for a patent claim to be patentable. An invention is not new and therefore not patentable if it was known to the public before the filing date of the patent application, or before its date of priority if the applicant claims priority of an earlier patent application. The purpose of the novelty requirement is to prevent prior art from being patented again. Definition Novelty is requirement for a patent claim to be patentable. In contrast, if an invention was known to the public before filing a patent application, or before its date of priority, if the priority of an earlier patent application is claimed, the invention is not considered new and therefore not patentable. To assess the novelty of an invention, a search through what is called the prior art is usually performed, the term "art" referring to the relevant technical field. A prior art search is generally performed with a view to proving that the invention is "not new" or old. No search can possibly cover every single publication or use on earth, and therefore cannot prove that an invention is "new". A prior art search may for instance be performed using a keyword search of large patent databases, scientific papers and publications, and on any web search engine. However, it is impossible to guarantee the novelty of an invention, even once a patent has been granted, since some little known publication may have disclosed the claimed invention. Rationale A patent grants an inventor a legally enforceable monopoly over their invention. This means that others can be legally restrained from exploiting the invention. It is not the intention of the patent system to deny anyone what they have been free to do before someone claims an invention. For example, one cannot patent the wheel, as that would exclude others from doing what they had previously been free to do. The legal test is that the invention must be something new, i.e. it must possess "novelty". The invention of the wheel is not new, because the wheel already forms part of the prior art. Specific concepts In some countries, such as the Australia, Canada, China, Japan, Russia, United States, a grace period exists for protecting an inventor or their successor in title from authorised or unauthorised disclosure of the invention before the filing date. That is, if the inventor or the successor in title publishes the