the 3 best definitions of ethics

ETHICS, the name generally given to the science of moral philosophy. The word " ethics " is derived from the Gr. r)OtKOS, that which pertains to rlOos, character.(ref.: http://www.1911encyclopedia.org/Ethics)

Ethics is a branch of philosophy which seeks to address questions about morality, such as what the fundamental semantic, ontological, and epistemic nature of ethics or morality is (meta-ethics), how moral values should be determined (normative ethics), how a moral outcome can be achieved in specific situations (applied ethics), how moral capacity or moral agency develops and what its nature is (moral psychology), and what moral values people actually abide by (descriptive ethics). (ref. wikipedia.com)

Ethics (used with a sing. verb) The study of the general nature of morals and of the specific moral choices to be made by a person; moral philosophy. (http://education.yahoo.com/reference/dictionary/entry/ethic;_ylt=AkLJc3RsGEGUWsifmkArMIysgMMF)