A Lieutenant is a military, paramilitary or police officer.
The word lieutenant derives from French; the lieu meaning "place" as in a position; and tenant meaning "holding" as in "holding a position"; thus a "lieutenant" is somebody who holds a position in the absence of his superior.
The British monarch's representative in Ireland and in the counties of the United Kingdom was/is called the Lord-Lieutenant. In French history, "lieutenant du roi" was a title borne by the officer sent with military powers to represent the king in certain provinces. It is in the sense of a deputy that it has entered into the names of more senior officers, Lieutenant General, Lieutenant Colonel, and Lieutenant Commander.
In the nineteenth century those 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."
The word is pronounced loo-tenant in American English and usually lef-tenant in British English. The Royal Navy, however, traditionally pronounce the word as l'tenant which is a closer anglicised approximation of the original French.
In Canada, lef-tenant is standard for all branches of the Armed Forces and for other usages such as lieutenant governor or Quebec lieutenant.
The British pronunciation is prevalent during 14th and 15th centuries with the word being variously spelled as lieftenant, lyeftenant or luftenant. It may have originated from a mistaken reading of the 'u' as a 'v', lev-tenant eventually becoming lef-tenant. Some sources state that the original French word lieu had an alternative form spelt and pronounced lieuf, and that the modern British English form retains the former spelling and the latter pronunciation.
It has also been speculated that it may have come from a fanciful etymology which associated it with the verb 'to leave', as the lieutenant only took up his duties once his superior officer had 'left'.
Another theory comes from the fact that in typical propriety the person or persons standing to the rear-left of a gentleman held power and were typically those directly second to him. The person or persons standing to the rear-right were considered to have no or less standing than those to the rear-left, such as aides, bodyguards, wives, etc., often holding this position for simple facility rather than societal importance. This tradition remains in military parades, with lieutenants standing to the rear-left of the commanding officer (when facing the advance.)
Duties and rankings
Originally, this was generally applied to what we today call just plain Lieutenant, who was taking the place of the Captain, who was the officer who actually raised the company of soldiers. The Lieutenant's job was to lead the soldiers into battle so that the Captain would not have to.
Most militaries have two types of Lieutenant:
Sometimes the rank of Third Lieutenant is used, typically as a cadet or temporary rank indicating that the holder is a commissioned officer in the chain of command—barely.
Note that a naval Lieutenant and Royal Air Force (UK) Flight Lieutenant are equivalent in rank to an army Captain, and a naval Lieutenant, Junior Grade (US) or Sub-Lieutenant (UK) is equivalent in rank to an army First Lieutenant. In the US Navy, a Lieutenant is a senior division officer on a ship, or a ship's department head.
Royal Navy Rank Insignia
The insignia of Sub-Lieutenant consists of one medium gold braid stripe (with loop) on a 'navy blue'/black background. The medium stripe contrasts with the thin stripe used on the center stripe for the grade of Lieutenant-Commander and the RNZN rank of Ensign. The Royal Air Force followed this example of braiding when developing their rank system (see Flying Officer). Interestingly, this insignia looks like the United States Navy grade of Ensign, even though its equivalent grade in the USN is actually Lieutenant Junior Grade.
The insignia of a Lieutenant consists of two medium gold braid stripes (top stipe with loop) on a 'navy blue'/black background. This pattern was copied by the United States Navy and the Royal Air Force for their equivalent ranks grades (see Flight Lieutenant). In the Royal Navy, unlike the United States Navy that uses different insignia to differentiate line officers from specialty officers, the Royal Navy places a different colour (known as 'lights') between the braids. Once various specialist officers had different colours, but these were abolished in 1955, except for scarlet for medical officers (introduced in 1863) and orange for dental officers (introduced in 1924), which are still used. The former colours were: light blue for navigating officers (1863–1867 only), and in the 20th century for instructor officers; white for paymaster officers (from 1863); purple for engineer officers (from 1863); silver grey for shipwright officers (from 1918); dark green for electrical officers (from 1918); maroon, later replaced by salmon pink, for wardmaster officers (commissioned medical assistants) (from 1918); and dark blue for ordnance officers (from 1918).