休 xiū

Treat 休 as half of a word, not a word you speak. Alone in modern Mandarin it sounds chopped off, like answering "I'm rest" in English. 休息 is what real people say. And here's a nice side effect: once 休息 is in your head, you'll start spotting 休 at the front of other words, quietly doing the same job — carrying the idea of "rest" while the second character tells you what kind of rest it is.

休息 covers any pause at all: sitting down, scrolling your phone, staring at the wall for ten minutes. Nobody has to be asleep for it. 睡觉 means eyes shut, in bed, gone. So if you say 我昨天休息了八个小时, a Chinese friend hears "I took an eight-hour break," which sounds like a weird flex. For real sleep, say 我睡了八个小时.

Lots of character origin stories get cooked up after the fact by people who never looked at the old writing. 休 isn't one of them. In oracle bone script it's drawn as a person standing next to a tree, and the meaning has never moved: stop, take a breather. The left piece is 亻, the flattened form of 人 (person). The right piece is 木 (tree). A guy and a trunk. That's the whole thing.