Lieutenant is a rank of the Canadian Army and Royal Canadian Air Force. The equivalent rank in the Royal Canadian Navy is "sub-lieutenant". A naval lieutenant is one rank superior to the army rank of lieutenant and the naval rank of sub-lieutenant. Lieutenants and sub-lieutenants are equivalent to ranks with a NATO code of OF-1. The British pronunciation "lef-tenant" is used by the Canadian Armed Forces, but the American pronunciation of "loo-tenant" is sometimes heard.