Lieutenant colonel is a rank of commissioned officers in the armies, most marine forces and some air forces of the world, above a major and below a colonel. Several police forces in the United States use the rank of lieutenant colonel. The rank of lieutenant colonel is often shortened to simply "colonel" in conversation and in unofficial correspondence. Sometimes, the term 'half-colonel' is used in casual conversation in the British Army. In the British military, it is customary to refer to either a Lieutenant Colonel or a Colonel by their first names when mentioning them, e.g "Colonel Tim will be at the parade". In the United States Air Force, the term 'light bird' or 'light bird colonel' is an acceptable casual reference to the rank but is never used directly towards the rank holder. A lieutenant colonel is typically in charge of a battalion or regiment in the army.