A Lieutenant is a military or paramilitary officer. The word lieutenant derives from French; the lieu meaning "place" as in a position or territory; and tenant meaning "holding" as in "holding a position". 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.
Pronunciation
The word is pronounced loo-tenant in American English and usually lef-tenant in British English although this is only correct with respect to the British Army. The Royal Navy traditionally pronounced 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. 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. 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'.
Most militaries have two types of Lieutenant:
Note that a naval Lieutenant is 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 1st Lieutenant. See Comparative military ranks
In the US Navy, a Lieutenant is a seinor division officer on a ship, or a ship's department head.
See also Lord-Lieutenant, military rankDuties 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.
Sometimes the rank of 3rd Lieutenant is used, typically as a cadet or temporary rank indicating that the holder is a commissioned officer in the chain of command -- barely.