Specialist

Specialist is the fourth enlisted rank in the UNSC Army and is the highest enlisted rank. It is equal in rank to Petty Officer Third Class in the UNSC Navy, and Corporal in the UNSC Marine Corps

The rank of Specialist is equal to that of a Corporal in the Army or Marine Corps. Though the rank of Corporal is considered the lowest Non-commissioned officer rank.

An example of a specialist is Healy, from Joseph Staten's novel, "Contact Harvest" who was their team's medic.