Unethical means violating accepted principles of right and wrong behavior, especially in professional or serious contexts. When a scientist falsifies research data to get better results, that's unethical because it betrays the trust that science depends on. When a business owner lies about their product to make more money, they're acting unethically.

The word often appears in situations involving rules, fairness, or trust. A doctor who shares private patient information without permission commits an unethical act, even if no law was broken. A journalist who makes up quotes is behaving unethically because journalism requires truthfulness.

The word unethical specifically refers to breaking the moral standards or codes that guide how people should act in certain roles or situations. A lawyer who helps a client lie under oath acts unethically. A student who plagiarizes a paper is doing something unethical because it violates academic integrity standards.

The opposite is ethical, meaning behavior that aligns with proper moral standards. Ethics are the principles themselves: a group might debate the ethics of using animals in medical research, trying to figure out what's right.