    lieutenant commander (also hyphenated lieutenant-commander and abbreviated lt cdr, ltcdr. or lcdr) is a commissioned officer rank in many navies. the rank is superior to a lieutenant and subordinate to a commander. the corresponding rank in most armies (armed services) and air forces is major, and in the royal air force and other commonwealth air forces is squadron leader. the nato rank code is mostly of-3. a lieutenant commander is a senior department officer or the executive officer (second-in-command) on many warships and smaller shore installation, or the commanding officer of a smaller ship/installation. they are also senior department officers in naval aviation squadrons. ==etymology== most commonwealth and other navies address lieutenant commanders by their full rank or the positions they occupy ("captain" if in command of a vessel). the united states navy, however, usually addresses officers using the higher grade of the rank. for example, a lieutenant, junior grade, is addressed simply as "lieutenant," and a lieutenant commander is addressed as "commander." ==origins== lieutenants were commonly put in command of smaller vessels not warranting a commander or captain. such a lieutenant was called a "lieutenant commanding" or "lieutenant commandant" in the united states navy, and a "lieutenant in command," "lieutenant and commander," or "senior lieutenant" in the royal navy. the usn settled on "lieutenant commander" in 1862 and made it a distinct rank. the rn followed suit in march 1914.{{cite web |title=lieutenant commander 
Military_ranks_of_Australia Military_ranks_of_Denmark Military_ranks_of_the_Royal_Navy Naval_ranks