Potential Complement vs 能: Two Kinds of 'Can' | Chinese (Mandarin) Grammar

English "can" is a single overworked word. Chinese splits the job in two, and learners feel the seam constantly. The potential complement — 听得懂 (tīng de dǒng), 拿得动 (ná de dòng), 进不去 (jìn bu qù) — asks one narrow question: does the action reach its result? The modal 能 (néng) is much broader: it covers permission, whether circumstances allow something, and raw capacity. The clearest way to feel the difference is a pair like 进不去 ("can't get in" — the door's locked, the room is packed) versus 不能进去 ("not allowed in" — there's a rule). Both are "can't go in" in English; Chinese would never confuse them.

The core split: result vs circumstance

Think of the potential complement as living inside the action. It fuses a verb with a result (懂 understand, 见 perceive, 动 budge, 完 finish, 到 reach) and then asks whether that result can come about — given your ability, the object, and the conditions all at once. 能, by contrast, floats outside the action as a modal, weighing in on whether you're permitted or whether the situation makes the action possible at all.

老师说得慢一点儿，我就听得懂了。

lǎoshī shuō de màn yìdiǎnr, wǒ jiù tīng de dǒng le

If the teacher speaks a bit slower, I can understand. (neutral) — 听得懂: the result 'understand' is reached.

这里能抽烟吗？

zhèlǐ néng chōuyān ma?

Is smoking allowed here? (informal) — pure permission, so 能; there's no result to attach a complement to.

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Ask yourself: "Is the action reaching a result (understand it, lift it, finish it), or is something outside the action — a rule, an opportunity, a general knack — at stake?" Result → potential complement. Rule / opportunity / capacity → 能.

When only the potential complement works

Whenever the point is whether an action hits its result, Chinese reaches for the potential complement, and 能 sounds wrong or incomplete. This is especially true of the crisp negatives every learner needs early: 听不懂 (can't make out), 看不见 (can't see), 找不到 (can't find), 买不起 (can't afford), 进不去 (can't get in). There is simply no idiomatic way to say these with 不能 alone — *不能懂 is not how the language expresses "can't understand."

他说的是方言，我一句也听不懂。

tā shuō de shì fāngyán, wǒ yí jù yě tīng bu dǒng

He's speaking dialect — I can't understand a word. (informal) — 听不懂, never *不能懂.

人太多了，我挤了半天也进不去。

rén tài duō le, wǒ jǐ le bàntiān yě jìn bu qù

It's so crowded — I pushed for ages and still couldn't get in. (informal) — physical impossibility: 进不去.

这个字太小，我看不清楚。

zhège zì tài xiǎo, wǒ kàn bu qīngchu

This character is too small, I can't see it clearly. (neutral) — the result 'see clearly' fails: 看不清楚.

For understanding specifically, the 得/不 + 懂 pattern is the idiomatic workhorse — see the resultative 懂 page for how 懂 behaves as a result.

When only 能 works

Flip to permission, circumstance, or a general "am I able," and 能 takes over. Use 能 when:

Permission is at stake: 你不能进去 ("you're not allowed in"), 这里能停车吗 ("can you park here?").
Circumstances decide it: 明天有事，我不能来 ("something's come up, I can't come").
There's no result complement to hang anything on: with a bare verb like 来 (come), 去 (go, in the sense of attend), 参加 (attend), you can't build a potential complement, so 能 does the work.

我明天有点儿事，可能来不了，也不能保证。

wǒ míngtiān yǒudiǎnr shì, kěnéng lái bu liǎo, yě bù néng bǎozhèng

I've got something on tomorrow — I probably can't make it, and I can't promise. (informal) — 能 for the modal 'can promise'.

没有票，你不能进去。

méiyǒu piào, nǐ bù néng jìnqù

Without a ticket, you're not allowed in. (neutral) — permission, so 不能进去 — a rule, not a locked door.

Line the two "can't get in" up side by side and the whole distinction snaps into focus:

Chinese	English	What blocks it	Kind of 'can'
进不去 (jìn bu qù)	can't get in	door's locked / too crowded	potential complement
不能进去 (bù néng jìnqù)	not allowed in	a rule forbids it	modal 能
听不懂 (tīng bu dǒng)	can't understand	skill / speech too hard	potential complement
不能听 (bù néng tīng)	mustn't / can't listen	not permitted, or no chance to	modal 能

The overlap zone — and combining 能 with a potential complement

Plenty of real sentences sit in between, and both are fine with a shade of difference. 你看得懂吗 ("can you read it?" — is your skill up to the result) and 你能看懂吗 ("are you able to read it?" — adds a hint of "given the chance/conditions") both work. When you want to foreground an enabling condition, Chinese happily stacks 能 in front of a full potential complement: 能 + V得 + result.

戴上眼镜，我就能看得懂了。

dài shàng yǎnjìng, wǒ jiù néng kàn de dǒng le

Once I put my glasses on, I can read it. (neutral) — 能 supplies the enabling condition, 看得懂 supplies the result.

你能不能看得懂这份合同？

nǐ néng bu néng kàn de dǒng zhè fèn hétong?

Are you able to make sense of this contract? (neutral) — A-not-A on 能, wrapped around the potential 看得懂.

The negative usually collapses to the crisp potential form, though: for "I can't understand it," native speakers say 我看不懂, not the heavier 我不能看懂. Reach for the plain potential negative whenever it exists.

Common Mistakes

1. Using 不能 where the crisp potential negative is idiomatic. For "can't understand / can't see / can't find," the potential form is the natural one.

❌ 老师说得太快，我不能懂。

Wrong — 'can't understand' is 听不懂, not *不能懂.

✅ 老师说得太快，我听不懂。

lǎoshī shuō de tài kuài, wǒ tīng bu dǒng

The teacher talks too fast, I can't understand. — 听不懂 is the idiom.

2. Using a potential complement for permission. A rule is 能/不能 territory; a potential complement can't express "allowed."

❌ 这里抽不了烟。（meaning: smoking is forbidden here）

Wrong for 'not permitted' — 抽不了烟 means you physically can't (no cigarettes, can't light up).

✅ 这里不能抽烟。

zhèlǐ bù néng chōuyān

You can't smoke here (it's not allowed). — permission needs 能.

3. Redundantly stacking 能 on a negative potential. 看不懂 already means "can't understand"; adding 不能 double-negates the sense.

❌ 这本书我不能看不懂。

Wrong — 看不懂 is already 'can't understand'; 不能 makes it contradictory.

✅ 这本书我看不懂。

zhè běn shū wǒ kàn bu dǒng

I can't understand this book. — one negative is enough.

4. Forgetting that 能 stacks in front, never inside. The order is 能 + V得 + result, not V得 + 能 + result.

❌ 我看得能懂这封信。

Wrong order — 能 goes before the whole potential complement.

✅ 我能看得懂这封信。

wǒ néng kàn de dǒng zhè fēng xìn

I'm able to read this letter. — 能 + 看得懂.

Key Takeaways

Potential complement = does the action reach its result? (听得懂, 拿得动, 进不去). 能 = permission, circumstance, or general capacity.
The textbook pair: 进不去 (can't physically get in) vs 不能进去 (not allowed in).
For "can't understand / see / find / afford," the crisp potential negative (听不懂, 看不见, 找不到, 买不起) is the idiom — not 不能.
When you need an enabling condition plus a result, stack them: 能 + V得 + result (能看得懂).
The negative usually collapses to the plain potential form: say 看不懂, not 不能看懂.

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