Ethics, sometimes known as moral philosophy, is a branch of philosophy that involves systematizing, defending and recommending concepts of right and wrong conduct. 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. Philosophical ethics investigates what is the best way for humans to live, and what kinds of actions are right or wrong in particular circumstances. Ethics may be divided into three major areas of study:Related fields are moral psychology, descriptive ethics, and value theory. Ethics seeks to resolve questions dealing with human morality—concepts such as good and evil, right and wrong, virtue and vice, justice and crime.