fight vs combat

fight and combat both are nouns.

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

As nouns, combat is a hyponym of fight; that is, combat is a word with a more specific, narrower meaning than fight:

Other hyponyms of fight include Armageddon, pitched battle, naval battle, armed combat, dogfight, assault.

As nouns, fight and combat are synonyms defined as:

Other synonyms of fight include fighting, scrap.

As verbs, combat is a hyponym of fight; that is, combat is a word with a more specific, narrower meaning than fight:

fight (noun)	combat (noun)
a hostile meeting of opposing military forces in the course of a war	an engagement fought between two military forces
the act of fighting; any contest or struggle	the act of fighting; any contest or struggle
a boxing or wrestling match
an aggressive willingness to compete
an intense verbal dispute

fight (verb)	combat (verb)
be engaged in a fight; carry on a fight	battle or contend against in or as if in a battle
fight against or resist strongly
make a strenuous or labored effort
exert oneself continuously, vigorously, or obtrusively to gain an end or engage in a crusade for a certain cause or person; be an advocate for