The Navy Enlisted Classification (NEC) system, of which the NEC coding system is a part, supplements the enlisted rating structure in identifying personnel on active or inactive duty and billets in manpower authorizations. NEC codes identify a nonrating wide skill, knowledge, aptitude, or qualification that must be documented to identify both people and billets for management purposes.
For example, the rating for a Navy Hospital Corpsman is HM. However, just holding the rating of HM does not tell us what specific medical job that person performs. However, if he/she held the NEC HM-8407, we could look at the below list and find out that the person is qualified as a Radiation Health Technician.