Merriam-Webster Collegiate Dictionary - ethic

 noun  Etymology: Middle English ethik, from Middle French ethique, from Latin ~e, from Greek ethike, from ethikos  Date: 14th century  1. plural but singular or plural in construction the discipline dealing with what is good and bad and with moral duty and obligation  2.  a. a set of moral principles ; a theory or system of moral values the present-day materialistic ~ an old-fashioned work ~ — often used in plural but sing. or plural in constr. an elaborate ~s Christian ~s  b. plural but singular or plural in construction the principles of conduct governing an individual or a group professional ~s  c. a guiding philosophy  d. a consciousness of moral importance forge a conservation ~  3. plural a set of moral issues or aspects (as rightness) debated the ~s of human cloning