OMT = Osteopathic manipulative therapy/OMM = osteopathic manipulative medicine, NMM = neuromusculoskeletal medicine. The AO Board of NMM accredits the special proficiency in OMM/OMT. As I understand it, you can think of NMM as the area of practice (although it aligns closely with PM&R with extra osteopathic principles and is usually taught alongside FM) and OMT/OMM just as a specific collection of procedures.