应该 / 该 (yīnggāi / gāi): Should | Chinese (Mandarin) Grammar

应该 (yīnggāi) is the Mandarin should — and, pleasingly for English speakers, it maps onto "should" almost one-to-one, including a quirk English shares. Both languages use "should" for two quite different things: advice ("you should rest") and inference ("he should be home by now"). 应该 does exactly the same double duty, so much of what you already know about English "should" transfers directly. The one thing to hold onto is strength: 应该 is advice, not a command. It is weaker than 得 (děi) and 必须 (bìxū), which push into "have to / must." If something is non-negotiable, 应该 will undersell it.

应该 for advice: "should / ought to"

The everyday use is advisability — what's the right, wise, or expected thing to do. This is the 应该 of giving advice, offering an opinion, or gently telling someone off.

你脸色不好，应该多休息，别太拼了。

nǐ liǎnsè bù hǎo, yīnggāi duō xiūxi, bié tài pīn le

You look pale — you should rest more and stop pushing yourself. (informal) — 应该 giving advice.

这么大的事，你应该早点告诉我。

zhème dà de shì, nǐ yīnggāi zǎodiǎn gàosu wǒ

Something this big — you should have told me sooner. (informal) — advice about the past, no extra tense marking.

他帮了这么大的忙，我们应该好好谢谢他。

tā bāng le zhème dà de máng, wǒmen yīnggāi hǎohǎo xièxie tā

He helped us so much — we ought to thank him properly. (neutral) — 应该 = 'ought to'.

Notice the second example: Chinese doesn't add a past marker to say "should have." 你应该早点告诉我 covers both "you should tell me earlier" and "you should have told me sooner"; context and the time word 早点 carry the sense. Don't try to bolt 了 onto 应该 to make it past.

应该 for inference: "should (by now) / must be"

The second reading is probability — a confident inference from what you know. 他应该到了 isn't advice; it's "he should be there by now (I reckon)." This is 应该 as a hedge just short of certainty.

现在都六点了，他应该到家了吧。

xiànzài dōu liù diǎn le, tā yīnggāi dào jiā le ba

It's already six — he should be home by now. (informal) — inferential 应该 + sentence-final 了.

都学了三年了，这个词他应该认识。

dōu xué le sān nián le, zhège cí tā yīnggāi rènshi

He's studied for three years — he should know this word. (neutral) — reasoning to a likely conclusion.

火车应该快到了，我们再等一会儿。

huǒchē yīnggāi kuài dào le, wǒmen zài děng yíhuìr

The train should be arriving soon — let's wait a bit more. (informal) — 应该 for an expectation.

💡

应该 hedges — it means "should / probably," not "definitely." If you're certain, use 一定 (yídìng, "must be, surely"): 他一定到了 "he's definitely there." 他应该到了 leaves room for doubt; 他一定到了 doesn't.

The colloquial short form 该 (gāi)

In speech, 应该 often shrinks to just 该 (gāi). It's more casual and turns up constantly in the 该…了 frame — "it's time to…," "one ought to… by now."

该走了，再不走就迟到了。

gāi zǒu le, zài bù zǒu jiù chídào le

Time to go — any later and we'll be late. (informal) — 该…了 = it's time to.

好了好了，孩子们该睡觉了。

hǎo le hǎo le, háizimen gāi shuìjiào le

Alright, alright — it's bedtime for the kids. (informal) — 该睡觉了.

这下你该相信我了吧？

zhè xià nǐ gāi xiāngxìn wǒ le ba?

Now you should believe me, right? (informal) — 该 as a pointed 'you really ought to'.

该 also does duty as "it's someone's turn": 该你了 (gāi nǐ le) — "your turn." Same core idea: it's due, it's what should happen next.

别发呆了，轮到你了，该你了！

bié fādāi le, lún dào nǐ le, gāi nǐ le!

Stop spacing out — it's your turn now! (informal) — 该你了 = it's your go.

Negation: 不应该

The negation is the regular 不应该 (bù yīnggāi), "shouldn't / ought not to." It works for both advice ("you shouldn't do that") and the moral "shouldn't have."

对不起，我不应该怀疑你。

duìbuqǐ, wǒ bù yīnggāi huáiyí nǐ

I'm sorry — I shouldn't have doubted you. (neutral) — 不应该, no past marker needed.

Reading	Pattern	Example	Gloss
advice	应该 + verb	你应该休息 (nǐ yīnggāi xiūxi)	you should rest
inference	应该 + verb (+ 了)	他应该到了 (tā yīnggāi dào le)	he should be there by now
it's time to (colloquial)	该 + verb + 了	该走了 (gāi zǒu le)	time to go
negation	不应该 + verb	你不应该去 (nǐ bù yīnggāi qù)	you shouldn't go

Common Mistakes

1. Using 应该 for hard, non-negotiable necessity. 应该 is advice. For a rule you can't break, use 得 (děi) or 必须 (bìxū) — see the obligation modals contrast.

❌ 登机前你应该出示护照，不然上不了飞机。

Too soft for a hard rule — this is a requirement, so use 必须 / 得, not 应该.

✅ 登机前你必须出示护照。

dēngjī qián nǐ bìxū chūshì hùzhào

You must show your passport before boarding. — 必须 for a firm rule.

2. Forgetting the 了 in 该…了. The "it's time to" reading needs the sentence-final 了. Without it, the sentence feels unfinished.

❌ 十二点了，该吃午饭。

Incomplete — for 'time for lunch' you need the closing 了: 该吃午饭了.

✅ 十二点了，该吃午饭了。

shí'èr diǎn le, gāi chī wǔfàn le

It's twelve — time for lunch. — 该…了.

3. Adding 了 to 应该 to make it past. "Should have" isn't marked on 应该; keep it bare and let a time word carry the tense.

❌ 你应该了早点来。

Wrong — 应该 doesn't take 了. Say 你应该早点来 ('you should have come earlier').

✅ 你应该早点来。

nǐ yīnggāi zǎodiǎn lái

You should have come earlier. — bare 应该 + the time word 早点.

4. Using 应该 when you actually mean "definitely." 应该 hedges; for certainty use 一定.

❌ 别担心，他应该会来，我百分之百确定。

Contradictory — 应该 hedges, so it clashes with '100% sure'. For certainty use 一定会来.

✅ 别担心，他一定会来。

bié dānxīn, tā yídìng huì lái

Don't worry — he'll definitely come. — 一定 for certainty.

Key Takeaways

应该 (yīnggāi) = English should, in both senses: advice (你应该多休息) and inference (他应该到了 "should be there by now").
It's advice, not command — weaker than 得 / 必须. For hard rules, upgrade to those.
The short form 该 (gāi) is colloquial, especially 该…了 "it's time to…" and 该你了 "your turn." Don't drop the 了.
Chinese doesn't mark "should have" with 了 — keep 应该 bare and let a time word (早点) carry the past.
Negation is 不应该; for certainty (not hedged probability) switch to 一定.

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