A lieutenant (abbreviated Lt, LT, Lieut and LEUT) is a junior commissioned officer in many nations' armed forces.
The rank of lieutenant has different meanings in different military formations (see comparative military ranks), but the majority of cases it is common for it to be subdivided into a senior (first lieutenant) and junior (second lieutenant) rank. In navies it may relate to a particular post rather than a rank. Typically, the post of lieutenant in naval usage is held by a captain, while still a junior officer rank, is senior to the army lieutenant rank. It is also used in fire services, emergency medical services, security services and police forces as a rank.
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 utilizing both such ranks. Notable uses include lieutenant governor in various governments, and Quebec lieutenant in Canadian politics.