fight vs fight back

fight is a noun but fight back is not a noun.

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

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

As verbs, fight and fight back are synonyms defined as:

Other synonyms of fight include defend, fight down, oppose.

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

fight (verb)	fight back (verb)
be engaged in a fight; carry on a fight	fight against or resist strongly
fight against or resist strongly	defend oneself
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