commander vs commanding officer

commander and commanding officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
commander	Yes	No	No	No
commanding officer	Yes	No	No	No

As nouns, commander and commanding officer are synonyms defined as:

commander and commanding officer: an officer in command of a military unit

Other synonyms of commander include commandant.

commander (noun)	commanding officer (noun)
an officer in command of a military unit	an officer in command of a military unit
a commissioned naval officer who ranks above a lieutenant commander and below a captain
an officer in the airforce
someone in an official position of authority who can command or control others