Osteopathic Postdoctoral Training Institution. All Osteopathic internship and residencies are part of a specific OPTI, which is a partnership between hospitals, osteopathic medical schools, and GME training programs.

Office of Productivity, Technology, and Innovation, part of the U.S. Department of Commerce. Relevant to metric history in that it took over the functions of the USMB after the USMB was dissolved, although those functions later moved to NBS.