Must (必须 vs 得)

Chinese has two common ways to say "must": 必须 (bìxū) and 得 (děi). While both translate to "must" or "have to" in English, they differ in tone and usage.

必须 is formal and strong. It expresses rules, obligations, and non-negotiable requirements: 学生必须穿校服 — "Students must wear school uniforms." 你必须在六点以前到 — "You must arrive before 6 o'clock." It carries authority and is common in written rules, instructions, and emphatic speech.

得 (děi — note the pronunciation, not dé or de) is casual and practical. It expresses personal necessity based on circumstances: 明天我得早起 — "I have to get up early tomorrow." 太晚了，我得走了 — "It's too late, I have to go." It feels like explaining what your situation requires rather than stating a rule.

The negative forms are different and important. 必须 negates with 不: 你不必须去 → more naturally, 你不必去 or 你不用去 (you don't have to go). 得 negates with 不用 (don't need to): 你不用担心 (You don't need to worry). Be careful: 不得 (bùdé) exists but means "must not / may not" — it is a prohibition, not simply the negative of 得 (děi).