What is the difference between an assignment and a license in patent law?

The MPEP distinguishes between assignments and licenses in patent law:

1. Assignment: ‘An assignment of a patent, or patent application, is the transfer to another of a party’s entire ownership interest or a percentage of that party’s ownership interest in the patent or application.’
2. License: ‘As compared to assignment of patent rights, the licensing of a patent transfers a bundle of rights which is less than the entire ownership interest, e.g., rights that may be limited as to time, geographical area, or field of use.’

The key difference is that an assignment transfers ownership, while a license grants permission to use the patent without transferring ownership. The MPEP further clarifies: ‘A patent license is, in effect, a contractual agreement that the patent owner will not sue the licensee for patent infringement if the licensee makes, uses, offers for sale, sells, or imports the claimed invention, as long as the licensee fulfills its obligations and operates within the bounds delineated by the license agreement.’