Generally, the terms ethics and morality are used interchangeably, although a few different communities (academic, legal, or religious, for example) will occasionally make a distinction. In fact, Britannica’s article on ethics considers the terms to be the same as moral philosophy. While understanding that most ethicists (that is, philosophers who study ethics) consider the terms interchangeable, let’s go ahead and dive into these distinctions.
(Read Peter Singer's Britannica entry on ethics.)
Both morality and ethics loosely have to do with distinguishing the difference between “good and bad” or “right and wrong.” Many people think of morality as something that’s personal and normative, whereas ethics is the standards of “good and bad” distinguished by a certain community or social setting. For example, your local community may think adultery is immoral, and you personally may agree with that. However, the distinction can be useful if your local community has no strong feelings about adultery, but you consider adultery immoral on a personal level. By these definitions of the terms, your morality would contradict the ethics of your community. In popular discourse, however, we’ll often use the terms moral and immoral when talking about issues like adultery regardless of whether it’s being discussed in a personal or in a community-based situation. As you can see, the distinction can get a bit tricky.
It’s important to consider how the two terms have been used in discourse in different fields so that we can consider the connotations of both terms. For example, morality has a Christian connotation to many Westerners, since moral theology is prominent in the church. Similarly, ethics is the term used in conjunction with business, medicine, or law. In these cases, ethics serves as a personal code of conduct for people working in those fields, and the ethics themselves are often highly debated and contentious. These connotations have helped guide the distinctions between morality and ethics.
Ethicists today, however, use the terms interchangeably. If they do want to differentiate morality from ethics, the onus is on the ethicist to state the definitions of both terms. Ultimately, the distinction between the two is as substantial as a line drawn in the sand.