Joint inventorship occurs when two or more individuals collaborate to create an invention. The MPEP provides guidance on joint inventorship based on 35 U.S.C. 116: "When an invention is made by two or more persons jointly, they shall apply for patent jointly and each make the required oath, except as otherwise provided in this title. Inventors may apply for a patent jointly even though (1) they did not physically work together or at the same time, (2) each did not make the same type or amount of contribution, or (3) each did not make a contribution to the subject matter of every claim of the patent." This means that joint inventors don't need to work together physically or contribute equally to be considered joint inventors. The key is that each inventor must contribute to the conception of at least one claim in the patent application. To learn more: joint inventorship patent application collaboration invention conception