ethic

Ethics and morals are both used in the plural and are often regarded as synonyms, but there is some distinction in how they are used.

Morals often describes one's particular values concerning what is right and what is wrong:

It would go against my morals to help you cheat on the test.

He appears to view himself as a kind of culture warrior, striking out against the crumbling morals of modern society.
Jonathan Goldsbie, Now Toronto, 16 Oct. 2014

While ethics can refer broadly to moral principles, one often sees it applied to questions of correct behavior within a relatively narrow area of activity:

Our class had a debate over the ethics of genetic testing.

Anybody, it seemed, could make the music -- if they couldn't play guitar, they could push a button -- and nobody worried about the ethics of appropriating riffs.
Jennifer Foote, Newsweek, 23 July 1990

In addition, morals usually connotes an element of subjective preference, while ethics tends to suggest aspects of universal fairness and the question of whether or not an action is responsible:

Perhaps you don’t like Kim Kardashian, or her family, or her morals don’t align with yours, or you just think it’s weird that she might have had some plastic surgery, likes to apply makeup in a really complicated way and named her kid “Saint.”
Sarah Boboltz, The Huffington Post, 12 Oct. 2016

The Frenches, both professors in The Media School, focused on the ethics of making medical decisions for a child who could not express her own wishes yet…
Chris Mura, Indiana Daily Student, 18 Oct. 2016