An officer was a member of a group typically in the areas of the military. An officer's typical role was to command and direct, maintain discipline, and make plans and provisions for operation. Certain organizations had special criteria for one to achieve the status of officer.
Commission
In military service, a commission was an order from the service's supreme authority, such as its commander-in-chief, authorizing an individual to legally hold a military rank, with all the privileges and responsibilities of said rank. A commission usually appointed an individual to hold an officer's rank. (TNG: "Where No One Has Gone Before", "Ménage à Troi")
In times of conflict, a temporary commission could appoint an officer to command rank to replace an incapacitated or killed commanding officer. (TNG: "The Battle"; DS9: "Valiant", "The Siege of AR-558") Commander William T. Riker, for example, was granted a field commission promoting him to Captain and given command of the USS Enterprise-D when the ship's commanding officer, Captain Jean-Luc Picard, was abducted and assimilated by the Borg during their first attempt to assimilate Earth. (TNG: "The Best of Both Worlds", "The Best of Both Worlds, Part II") Before this, Riker had repeatedly turned down commissions to captain various vessels to remain aboard the Enterprise and was considering turning down captaincy of the USS Melbourne. (TNG: "The Best of Both Worlds")
In situations where contact with Starfleet was not possible for very extended periods, a commanding officer had the authority to grant commissions to officers under their command, or revoke existing commissions; that is, they had the authority to promote or demote their officers. (VOY: "Caretaker", "Parallax", "Thirty Days") Examples of this are when Captain Kathryn Janeway, commanding officer of the USS Voyager, promoted her chief tactical officer and security chief, Lieutenant Tuvok, to the higher rank of lieutenant commander, or when she demoted her flight controller, Lieutenant junior grade Tom Paris, to ensign. (VOY: "Revulsion", "Thirty Days") After a year of exemplary service, she reinstated him to his former rank. (VOY: "Unimatrix Zero")
Within the Takret Militia resigning a commission was not tolerated. In 2152, the three Takret Rellus Tagrim, Renth, and Guri requested shelter aboard Enterprise NX-01 to prevent their superiors finding them. (ENT: "The Catwalk")
Starfleet
In the Federation Starfleet, an officer or commissioned officer was an individual who had attended and graduated from the four-year cadet program of Starfleet Academy. (TNG: "The Drumhead"; DS9: "Starship Down", "Little Green Men", "Homefront", "Paradise Lost") Upon graduation from the Academy, the cadet was granted a commission appointing him or her to the rank of Ensign, or in exceptional circumstances Lieutenant junior grade. (TNG: "The Pegasus"; VOY: "Caretaker", "Non Sequitur"; DS9: "Favor the Bold", "Valiant", "What You Leave Behind") Trades such as Doctor or Counselor graduated as a Lieutenant junior grade as standard due to the extra time spent studying before graduating. (TNG: "Tin Man", "Conundrum", "Ethics")
Commissioned officers and enlisted officers were distinguished from other crewmembers through the use of a rank structure. (Star Trek: The Next Generation; Star Trek: Deep Space Nine)
Commissioned officer rank structure
Starfleet ranks from lowest to highest:
- Ensign
- Lieutenant junior grade
- Lieutenant
- Lieutenant commander
- Commander
- Captain
- Fleet captain
- Commodore
- Rear admiral
- Vice admiral
- Admiral
- Fleet admiral
Other officer terms
- Certain officer positions could be filled by non-commissioned officers and civilians if the need arose.
By rank
By title
- Senior officer (see also: senior staff)
- Junior officer (see also: Staff officer)
- First officer
- Second officer
- Third officer
By command structure
By department or function
- Archaeology and anthropology officer
- Armory officer
- Bridge officer
- Communications officer
- Engineering officer
- Helm officer
- Intelligence officer
- Deputy intelligence officer
- Liaison officer
- Medical officer
- Mess officer
- Morale officer
- Operations officer
- Personnel officer
- Police officer
- Records officer
- Science officer
- Security officer
- Strategic operations officer
- Tactical officer
- Weapons officer