ethics vs casuistry

ethics and casuistry both are nouns.

Word	Noun	Adjective	Verb	Adverb
ethics	Yes	No	No	No
casuistry	Yes	No	No	No

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

ethics: the philosophical study of moral values and rules
casuistry: moral philosophy based on the application of general ethical principles to resolve moral dilemmas

Other hyponyms of ethics include bioethics, endaemonism, eudemonism, hedonism, ethical nihilism, moral nihilism.

ethics (noun)	casuistry (noun)
the philosophical study of moral values and rules	moral philosophy based on the application of general ethical principles to resolve moral dilemmas
motivation based on ideas of right and wrong	argumentation that is specious or excessively subtle and intended to be misleading