duel vs fight

duel and fight both are nouns.

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

As nouns, fight is a hypernym of duel; that is, fight is a word with a broader meaning than duel:

duel: a prearranged fight with deadly weapons by two people (accompanied by seconds) in order to settle a quarrel over a point of honor
fight: the act of fighting; any contest or struggle

Other hypernyms of duel include combat, fighting, scrap.

As verbs, fight is a hypernym of duel; that is, fight is a word with a broader meaning than duel:

Other hypernyms of duel include contend, struggle.

duel (noun)	fight (noun)
a prearranged fight with deadly weapons by two people (accompanied by seconds) in order to settle a quarrel over a point of honor	a hostile meeting of opposing military forces in the course of a war
any struggle between two skillful opponents (individuals or groups)	the act of fighting; any contest or struggle
	a boxing or wrestling match
	an aggressive willingness to compete
	an intense verbal dispute

duel (verb)	fight (verb)
fight a duel, as over one's honor or a woman	be engaged in a fight; carry on a fight
	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