Joint inventor or co-inventor means any one of the individuals who invented or discovered the subject matter of a joint invention or discovery. More than one inventor can be named on a United States patent, and the concept is explicitly recognized in the U.S. Code (U.S.C.). In the case of joint inventors, it is not necessary for the inventors to “physically work together or at the same time,” “make the same type or amount of contribution,” or “make a contribution to the subject matter of every claim of the patent” (35 U.S.C. 116). As such, it has been a matter for the courts to establish guidelines. Furthermore, joint inventors need not make a contribution to the subject matter of every claim in the patent. As a result, inventorship is determined on a claim-by-claim basis.