Prior art is a term used in patent law to broadly describe the entire body of knowledge from the beginning of time to the present. Prior art is everything publicly known before the invention, as shown in earlier patents and other published material. It is a barrier to obtaining a patent.
A patent is barred if the invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country, before or more than one year prior to the date of the application for patent in the United States. In analyzing an existing patent or in deciding whether to file a patent application for an invention, it is almost always necessary to consider the prior art.