Formal:
* Ethics: This is a very common synonym, referring to a set of principles about right and wrong.
* Values: These are beliefs about what is important or desirable.
* Principles: These are fundamental truths that guide behavior.
* Code of conduct: This refers to a set of rules or guidelines for behavior.
* Ethical guidelines: Similar to a code of conduct, but with more emphasis on ethical considerations.
Informal:
* Right and wrong: A simple, direct way to express the concept.
* Do's and don'ts: This is a more casual way to refer to rules or guidelines.
* What's right: This is a concise way to express the concept of moral standards.
The best word to use depends on the context and the specific nuance you want to convey.