fighting vs combat

fighting and combat both are nouns.

Word	Noun	Adjective	Verb	Adverb
fighting	Yes	Yes	No	No
combat	Yes	No	Yes	No

As nouns, fighting and combat are synonyms defined as:

Other synonyms of fighting include fight, scrap.

fighting (noun)	combat (noun)
the act of fighting; any contest or struggle	an engagement fought between two military forces
	the act of fighting; any contest or struggle

fighting (adjective)	combat (adjective)
engaged in or ready for military or naval operations

fighting (verb)	combat (verb)
	battle or contend against in or as if in a battle