Some of the general categories of military occupational specialty in the U.S. Army include administrative support, intelligence, law enforcement, combat and medical. Any primary job performed by an enlisted member of the Army is considered a military occupational specialty.
There are over 30 different branches of job category, each with one to about 30 different specialties. Some fields are very small, such as the Cyber branch, which has only the Cyber Operations Specialist specialty for enlisted members. The Ammunition, Mechanical Maintenance and Ordinance branch is one of the largest for enlisted members, with over 30 different specialties such as Bradley Fighting Vehicle System Maintainer, Radio & Communications Security and PATRIOT System Repairer. Medical is another large branch with specialties in many different types of patient care and facility support roles such as Biomedical Equipment Specialist, Operating Room Specialist, Veterinary Food Inspection Specialist and Behavioral Health Specialist.
Enlisted Army members are given a three-character military occupational specialty code for every phase of their career, even when they are not assigned to a particular job. There are military occupational specialty codes for being a trainee in various programs, for example. These codes consist of two digits with a letter appended. Warrant officers have their own unique code called the WOMOS, these consist of three digits followed by a letter.