Lieutenant is the last line officer rank deemed to be a 'junior officer', ranking above Lieutenant, Junior Grade and below a Lieutenant Commander. It has a ranking code of O-3 and is equivalent to a Marine Captain in the Starfleet Marine Corps. The rank insignia consists of two full pips.
The word lieutenant derives from French; the lieu meaning "in place" as in a position (like in lieu of); and tenant meaning "holding" as in "holding a position"; thus a "lieutenant" is somebody who holds a position in the absence of his or her superior. Similar words in other languages include the Arabic mulāzim (Arabic: ملازم), meaning "holding a place", and the Hebrew word segen (Hebrew: סגן), meaning "deputy" or "second to".
In the nineteenth century, British writers who either considered this word an imposition on the English language, or difficult for common soldiers and sailors, argued for it to be replaced by the calque "steadholder." However, their efforts failed, and the French word is still used, along with its Lieutenant Colonel variation.
Since at least 1580, the Lieutenants in a ship had been the officers immediately subordinate to the Commanding Officer (Captain). Before the English Restoration, Lieutenants were appointed by their Captains, and this inevitably led to abuses and to the widespread appointment of men of insufficient qualification. In 1677 Samuel Pepys introduced the first exam for Lieutenant, and it is from the date of this exam that their seniority was set. Lieutenants were numbered by their seniority within the ship, so that a frigate, which was entitled to three lieutenants, would have a First Lieutenant, a Second Lieutenant and a Third Lieutenant. A first-rate was entitled to six, and they were numbered accordingly. At first a Lieutenant's commission was given only for the ship in which he served, but after the loss of HMS Wager in 1741 and the subsequent mutiny, Lieutenants were given full commissions upon passing their examination.
During the early days of the naval rank, a Lieutenant might be very junior indeed, or might be on the cusp of promotion to Captain; by modern standards he might rank with any marine rank between Second Lieutenant and Lieutenant Colonel. As the rank structure of navies stabilized, and the ranks of Commander, Lieutenant Commander and Lieutenant Junior Grade were introduced, the naval Lieutenant came to rank with a Marine Captain.
Lieutenants are most commonly billeted as Department Heads aboard a starship or starbase. Occasionally, in lieu of a more senior officer, a Lieutenant may temporarily command a small starship, though this is rare and usually only done in emergency circumstances. Often, a Lieutenant may hold command of a team within a department - a security detail, or engineering team, for example.
|Starfleet Officer Ranks|
|Ensign||Lieutenant, Junior Grade||Lieutenant||Lieutenant Commander||Commander||Captain||Fleet Captain||Commodore||Rear Admiral||Vice Admiral||Admiral||Fleet Admiral|