Private, First Class
From Halopedia, the Halo wiki
Private, First Class, abbreviated to PFC, is a Enlistment rank of E-2 in the United Nations Space Command Unified Ground Command (UNICOM) rank structure. It is preceded by Private and subordinate to a Lance Corporal.
- Halo: Official Spartan Field Manual - PART 8: UNSC ORGANISATION, UNICOM Ranks, page 142-143