commander in chief vs commander-in-chief

commander in chief and commander-in-chief both are nouns.

Word	Noun	Adjective	Verb	Adverb
commander in chief	Yes	No	No	No
commander-in-chief	Yes	No	No	No

As nouns, commander in chief and commander-in-chief are synonyms defined as:

commander in chief and commander-in-chief: the officer who holds the supreme command

Other synonyms of commander in chief include generalissimo.

commander in chief (noun)	commander-in-chief (noun)
the officer who holds the supreme command	the officer who holds the supreme command