Commissioned Officers

Fleet Admiral is the highest attainable rank in Starfleet. Fleet Admirals, Admirals, Vice Admirals, and Rear Admirals are addressed as "Admiral", not Rear, Vice, etc.

Commodores are addressed as "Commodore".

Captains and full Commanders are addressed as "Captain" and "Commander", respectively.

A Lieutenant Commander is addressed as "Commander" as well.

At his pleasure, a Commander and above may address a Lieutenant Commander as "Mister", but he should know that he is giving offense to the officer by implying that he is a junior officer.

The Commanding Officer of a vessel is called "Captain" in direct address, regardless of grade. Some smaller ships have captains which are not Captains; however, while on their vessels they are addressed as "Captain".

Junior officers are addressed either by their ranks or as "Mister Smith". They should refer to each other in this manner.

At the pleasure of senior officers, female junior officers may be called "Ms. Smith".

Officers with the rank Lieutenant Junior Grade are addressed as "Lieutenant" when addressed by their rank.

Marine Commissioned Officers

Marines are addressed by their rank. They are not called "Mister".

All Generals, regardless of their rank, are addressed as "General", not "Major General", "Brigadier General", etc.

In direct address, Lieutenant Colonel's are called "Colonel" and Second Lieutenant's are called "Lieutenant".

Note that a Marine Captain is roughly equivalent to a Starfleet Naval Lieutenant. The "honorary" rank of "Major" to said marines while on naval vessels is ignored as the marines are generally referred to as "Marine Captain" to avoid confusion with the naval Captain of the ship.

By Starfleet tradition, the Marine Commanding Officer defers to the Naval Commanding Officer when aboard ship, and is generally outranked by him (although this is sometimes reversed for large contingents in some operations).

Warrant Officers

Warrant Officers hold their position by "warrant", and are considered to outrank all Enlisted grades.

WOs are generally found heading sub-departments such as Transporter Mechanisms or Shuttle Maintenance.

Enlisted Crewmen

Enlisted crewmen are addressed solely by their rank or by the word "Crewman".

Enlisted Crewmen can be called by last names, without "Mister" attached.

All "Crewmen" and "Privates" are called such, regardless of their grades, and all Naval Enlisted Crewmen of grades Petty Officer Third Class to Petty Officer First Class are called "Petty Officer".

All enlisted personnel of grades Chief Petty Officer to Master Chief Petty Officer are addressed as "Chief".