A lieutenant (UK: /lɛfˈtɛnənt/ lef-TEN-ənt, US: /luː-/ loo-;[1] abbreviated Lt., Lt, LT, Lieut and similar) is a junior commissioned officer rank in the armed forces of many nations, as well as fire services, emergency medical services, security services and police forces.
The rank in armies and air forces is often subdivided into subcategories of seniority. In English-speaking navies, lieutenants are often equivalent to the army rank of captain; in other navies, the lieutenants are usually equal to their army counterparts.
Lieutenant may also appear as part of a title used in various other organisations 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 organisation using both ranks.
Political uses include lieutenant governor in various governments, such as the viceregal representatives of the Crown in Canadian provinces. In the United Kingdom, a lord lieutenant is the sovereign's representative in a county or lieutenancy area, while a deputy lieutenant is one of the lord lieutenant's deputies.