Day 20: Have to, should, must not

★ 得 děi · 必须 · 应该 · ⚠️ 不用 vs 不能 — the pair that reverses · 25 min

Three ways to say must, one to say should, and ⚠️ one negation trap that works exactly like German's nicht müssen and Korean's -도 돼요:

你不用来。 — You don't have to come. 你不能来。 — You must not come.

★ And the negative of 得 is not 不得. Section 3 — this is the part that catches everyone.

1. ★ The three "must"

⚠️ ★ 得 is pronounced děi here, not dé or de. Same character, three readings: de (a particle you meet on Day 27), dé (to obtain), and ★ děi (must). This is the most-mispronounced common character in Chinese.

★ 得 vs 必须 is a register difference, not a meaning one. 得 is "I gotta"; 必须 is "it is required that". In speech, use 得. On a sign, expect 必须.

★ 我得走了 is the phrase to have ready — it is how you leave any conversation politely. (The 了 marks the change of situation; Day 26 explains it.)

2. ★ 应该 — should

★ 应该 also means "probably / ought to be" — 他应该在家。 (He should be at home = he probably is.) Same word, and context separates them easily.

最好 zuìhǎo = had better, best to — 你最好早点儿去。 (You'd better go early.)

3. ⚠️★★ The negatives — and 得 has none

### 得 has NO negative form. Use 不用 or 不必 instead.

⚠️ 不得来 is not a sentence. (不得 exists in formal written Chinese meaning "may not", which makes it worse — just use 不用.)

★★ And here is the reversal

### 不用 = you DON'T HAVE TO · 不能 = you MUST NOT

★ English "don't have to" and "must not" are far apart in meaning and close in shape. Chinese is the same. Telling a friend 你不能来 when you meant 你不用来 is a genuinely bad thing to get wrong.

★ 不用 is also the polite refusal from Day 19 — 不用了,谢谢. ★ Same word doing both jobs: "no need."

4. Permission and prohibition in the wild

★ 不行 bù xíng = "that won't do / no" — the flat refusal, and the natural opposite of 可以. 行 xíng on its own means "OK, fine" and is extremely common: — 六点行吗? — 行!

On signs

5. Dialogue

Alex: 请问,这儿可以拍照吗?工作人员: 不行,这儿不能拍照。那边可以。Alex: 好的。包呢? 我得存包吗?工作人员: 大包必须存。小包不用。Alex: 要给钱吗?工作人员: 不用,免费的。Alex: 谢谢。几点关门?工作人员: 六点。您六点以前必须出来。Alex: 好。鞋要脱吗?工作人员: 不用脱。Alex: 明白了,谢谢!(后来)小明: 你今天晚上有空吗?Alex: 不好意思,我得工作。明天可以吗?小明: 可以。那你最好早点儿睡。Alex: 你说得对。我该走了。

★ All four shapes, explicitly contrasted:不能拍照 (banned) · 必须存 (required) · 不用 (not required) · 不用脱 (not required).★ And 我得工作 / 我该走了 — 得 and 该 (short for 应该), both everyday spoken forms.

6. Exercises

A. ★ 得, 必须, or 应该?

1. I have to go. (casual) → 我___走了。
2. You must bring your passport. (a rule) → ___带护照。
3. You should see a doctor. → 你___去看医生。
4. I have to work. (casual) → 我___工作。

B. ⚠️★ Which one?

1. You don't have to come. → 你___来。
2. You must not come. → 你___来。
3. You don't have to pay. → ___给钱。
4. No photos. → ___拍照。

C. Ask permission.

1. May I take a photo? 2. May I sit here? 3. Can I try it? 4. Is that OK?

D. Refuse.

1. That won't do. 2. No thanks, no need. 3. You can't smoke here.

E. Read the sign.

1. 禁止吸烟 2. 禁止停车 3. 请勿拍照 4. 小心

F. ⚠️★ How is 得 pronounced here?

1. 我得走了。 2. 得到 (to obtain)

G. ⚠️ Fix the mistake.

1. 我不得来。
2. 你不能来。 (meaning: you don't have to)
3. 我得走了。 (read it aloud — which tone?)
4. (declining an offer) 不要!

7. Today's 10 sentences (flashcards)

1. 我得走了。 Wǒ děi zǒu le. — I have to go
2. 我得工作。 — I have to work
3. 必须带护照。 — You must bring your passport
4. 你应该去看医生。 — You should see a doctor
5. 你不用来。 — You don't have to come
6. 不用给钱。 — You don't have to pay
7. 这儿不能拍照。 — You can't take photos here
8. 可以拍照吗? — May I take a photo?
9. 不行。 — No / that won't do
10. 不用了,谢谢。 — No thanks, no need

8. 📲 Upload to LangNote

Upload section 3 (the reversal) and section 7 → study language Chinese.

★ Tomorrow is the week 3 review. Bring your Day 14 numbers — especially the tone percentage.

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