(in pl, but treated as sing. or pl) the principles of conduct governing an individual or a group
professional ethics
a set of moral principles or values
the current materialistic ethic
(in pl) the moral uprightness of an action, judgment, etc
I'm not sure of the ethics of this decision
(in pl, but treated as sing.) the study of the nature and basis of moral principles and judgments
We speak of ethics in two ways, descriptive and normative. The ethics of a group (Western ethics, business ethics) is the broad pattern of social behaviour and shared self-understanding that in fact knits the group together. When we say that an action would not be ethical, however, we mean that it would be wrong, not just that it is at odds with the ethics of some group. The remark ‘We don't do things that way’ hovers between these two poles — Professor Jonathan Dancy
ethicist /-sist/ noun
[Middle English ethik via French and Latin from Greek ēthikē, from ēthikos, from ethos custom, character]