The Navy Enlisted Classification (NEC) system supplements the rating designators for enlisted members of the United States Navy. A Naval rating and NEC designator are similar to the Military Occupational Specialty (MOS) designators used in the U.S. Army and U.S. Marine Corps. In military service, an enlisted rank is generally any rating below that of a commissioned officer. ... The United States Navy (USN) is the branch of the United States armed forces responsible for conducting naval operations around the globe. ... A Military Occupational Specialty (MOS) is a job classification in use in the U. S. Army and the U. S. Marine Corps. ... The Army is the branch of the United States armed forces which has primary responsibility for land-based military operations. ... United States Marine Corps Emblem The United States Marine Corps (USMC) is the second smallest of the five branches of the United States armed forces, with 170,000 active and 40,000 reserve Marines as of 2002. ...

The U.S. Navy has several ratings or job specialities for its enlisted members; see List of United States Navy ratings for more details. The United States Navy classifies its enlisted personnel with a system of rating (job speciality) and rate (military rank). ...

An enlisted member is known by the enlisted rating, for example, a Machinist's Mate (or MM), and/or by the enlisted rate, for example Petty Officer First Class (or PO1). Often Navy enlisted members are addressed by a combination of rating and rate. In this example, this machinist's mate petty officer first class may be addressed as Machnist's Mate 1st Class (or MM1). Machinists Mate is a rating in the United States Navys engineering community. ...

However, the NEC designator is a four-digit code that identifies skills and abilities beyond the standard (or outward) rating designator. According to the Military Personnel Manual (MILSPERMAN) 1221-010, the NEC designator facilities personnel planning, procurement, and selection for training; development of training requirements; promotion, distribution, assignment and the orderly call to active duty of inactive duty personnel in times of national emergency or mobilizaton.

For example, a person holding the MM-3385 is a nuclear-trained machinist's mate for surface ships. While a person with a MM-3355 is a nuclear-trained machinist's mate for submarines.

In the U.S. Navy's officer ranks, the naval officer designator serves as similiar purpose. See List of Naval Officer Designators for more details. The following is a partial list of current United States Naval Officer Community Designations: An officer designator describes their general community or profession. ...