Ethics, sometimes known as philosophical ethics, ethical theory, moral theory, and moral philosophy, is a branch of philosophy that involves systematizing, defending and recommending concepts of right and wrong conduct, often addressing disputes of moral diversity. The term comes from the Greek word ἠθικός ethikos from ἦθος ethos, which means "custom, habit". The superfield within philosophy known as axiology includes both ethics and aesthetics and is unified by each sub-branch's concern with value.