Must: 得 (děi) and 不用
得, pronounced děi, means "must / have to" in everyday speech: 我得走了 "I've got to go", 你得多休息 "you have to rest more". Yes, it's the same character as the complement-得 (de) in 说得很好 — the meaning depends on where it sits: before a verb it's děi "must".
The negative is its own word: 不用 (búyòng) "don't need to": 明天不用上课 "no class tomorrow". Never say 不得 for "don't have to" — the opposite of "must" in Chinese is "no need".
Examples
Common mistakes
Related grammar points
Practice this pattern in graded stories like The Saturday Surprise (Part 1), An Unexpected Discovery (Part 3), The Model Has a Problem (Part 2) inside the Literate Chinese app.
