commanding officer vs commandant

commanding officer and commandant both are nouns.

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

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

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

Other synonyms of commanding officer include commander.

commanding officer (noun)	commandant (noun)
an officer in command of a military unit	an officer in command of a military unit