Mulatto is an old, offensive word for a person with one Black parent and one white parent. Do not use it. It belongs to a time when people in power sorted human beings into racial boxes, and this box was one of them. The word is insulting not only because it is outdated, but because it was built from the word for a mule — an animal with mixed parentage — as if a person were a kind of hybrid livestock. That is a cruel idea, and it still hurts. You may meet the word in old books, old laws, or ugly speech. If you must talk about the idea, say “a person with one Black parent and one white parent,” or use the words the person themselves uses. Though actually, even a wide modern phrase like “mixed-race” is not a polite swap-in for this one word, which is narrower and much nastier. Never use it as a joke, a history-quiz label for a living person, or a “more precise” term.