This article is about the senior OF1/OF1a rank in English-speaking armed forces. For the more junior OF1/OF1b rank in Austrian, German and Swiss forces, see Leutnant.A lieutenant (abbreviated Lt. LT. Lieut. and LEUT.) is a junior commissioned officer in many nations' armed forces, fire service, or law enforcement.\r The meaning of lieutenant differs in different military formations (see comparative military ranks), but is often subdivided into senior (first lieutenant) and junior (second lieutenant) ranks. In navies it is often equivalent to the army rank of captain; it may also indicate a particular post rather than a rank. The rank is also used in fire services, emergency medical services, security services and police forces.\r Lieutenant may also appear as part of a title used in various other organizations with a codified command structure.It often designates someone who is second-in-command, and as such, may precede the name of the rank directly above it. For example, a lieutenant master" is likely to be second-in-command to the master in an organization using both ranks.