Crewman

Crewman was an enlisted rank of often limited responsibility or entry level duties, used by service organizations in various cultures, including Starfleet. The crewman rank was further divided into ranks: First Class, Second Class, and Third Class. These typically were more of a sign of years of service rather than ability or achievement.
Crewman were the least autonomous part of a Federation starship, often being part of a work team underneath a Petty Officer or commissioned Officer. Those that were not explicitly under a supervisor's watch received automated assignments from the ship's computer, typical for areas like Janitorial and Housekeeping departments on larger ships.