In the United States Army and Marine Corps, a is a job code used to identify a service member's specific role and duties.

In electronics, refers to a specific semiconductor structure that serves as the foundation for modern digital devices. Military Occupational Specialty | MOS - Marines

Related specialties are often grouped into Career Management Fields (CMFs) to help manage diverse roles across the force.

MOS codes are typically alphanumeric. For example, in the Army, 11B designates an Infantryman, while 68W identifies a Combat Medic.