A person having ordinary skill in the art (often abbreviated PHOSITA in the United States) — also referred to as the person of ordinary skill in the art, the person skilled in the art, or the man skilled in the art — is a legal fiction found in many patent laws throughout the world. This fictional person is considered to have the normal skills and knowledge in a particular technical field, without being a genius. He or she mainly serves as a reference for determining, or at least evaluating, whether an invention is non-obvious or not (in U.S. patent law), or does involve an inventive step or not (in European patent laws). If it would have been obvious for this fictional person to come up with the invention while starting from the prior art, then the particular invention is deemed not patentable.
In some patent laws, the person skilled in the art is also used as a reference in the context of other criteria, for instance in order to determine whether an invention is sufficiently disclosed in the description of the patent or patent application (sufficiency of disclosure is a fundamental requirement in most patent laws), or in order to determine whether two technical means are equivalents when evaluating infringement.
In practice, this legal fiction is actually a set of legal fictions which evolved over time and which may be differently construed for different purposes. It may be said that this legal fiction basically translates the need for each invention to be considered in the context of the technical field it belongs to.