moral nihilism vs ethics

moral nihilism and ethics both are nouns.

Word	Noun	Adjective	Verb	Adverb
moral nihilism	Yes	No	No	No
ethics	Yes	No	No	No

As nouns, ethics is a hypernym of moral nihilism; that is, ethics is a word with a broader meaning than moral nihilism:

moral nihilism: the meta-ethical view that nothing is intrinsically moral or immoral.
ethics: the philosophical study of moral values and rules

Other hypernyms of moral nihilism include moral philosophy.

moral nihilism (noun)	ethics (noun)
the meta-ethical view that nothing is intrinsically moral or immoral.	the philosophical study of moral values and rules
	motivation based on ideas of right and wrong