English speakers tend to run their whole middle-of-the-road confidence through two words, "probably" and "maybe," and let intonation do the rest. Chinese asks you to be more precise. It offers a graded ladder of certainty adverbs, and choosing the right rung is not decoration — a native listener hears exactly how sure you are from the word you pick. Reach reflexively for 可能 every time and you will sound permanently on the fence; the skill is to calibrate. This page is the master map. It lines the rungs up from most to least sure, gives each a natural example, and points you to the dedicated pages where the trickier members are treated in full.
The ladder at a glance
| Rung | Adverb | Rough confidence | Register / flavour |
|---|---|---|---|
| certain | 一定 / 肯定 (yídìng / kěndìng) | ~95–100% | neutral; firm |
| reasoned "should" | 应该 (yīnggāi) | ~80% | neutral; inference from evidence |
| probably | 大概 (dàgài) | ~70% | neutral, everyday |
| probably (unwelcome) | 恐怕 (kǒngpà) | ~70% | apologetic; braces for bad news |
| maybe | 可能 (kěnéng) | ~50% | neutral, all-purpose |
| perhaps | 也许 (yěxǔ) | ~50% | neutral, slightly bookish |
| who knows | 说不定 (shuōbudìng) | ~40%, often hopeful | colloquial, lively |
To feel the scale, hold the situation fixed and change only the adverb. Below, the question is always the same — is he home? — and each rung reports a different amount of confidence.
Top rung: 一定 / 肯定 — "definitely"
At the top, you are not guessing; you are drawing a firm conclusion from evidence. 一定 (yídìng) and its slightly more clinical partner 肯定 (kěndìng) both say "it must be so."
他一定在家，灯还亮着呢。
tā yídìng zài jiā, dēng hái liàng zhe ne
He's definitely home — the light's still on. (informal) — 一定 as an inference from evidence.
这么大的公司，他们肯定有这方面的经验。
zhème dà de gōngsī, tāmen kěndìng yǒu zhè fāngmiàn de jīngyàn
A company this big — they're certain to have experience in this area. (neutral)
Watch the boundary with 一定要 (yídìng yào): plain 一定 reports certainty, but 一定要 turns into insistence or obligation ("you absolutely must"). The full split is on the dedicated page for 一定 / 肯定.
Upper-middle: 应该 — the reasoned "should"
One step down from certainty sits 应该 (yīnggāi). It is the "should" of inference: given what you know, this is what you'd expect — a confident guess that stops short of a guarantee. English "he should be home by now" catches it exactly.
都八点了，他应该到公司了吧。
dōu bā diǎn le, tā yīnggāi dào gōngsī le ba
It's already eight — he should be at the office by now, right? (informal) — reasoned expectation, softened by 吧.
应该 also carries a separate "ought to" (moral) sense; that thread lives on the 应该 / 该 (should) page. On this scale we mean only the epistemic "should probably."
The middle: 大概 / 可能 — "probably / maybe"
This is the band English speakers overuse. 大概 (dàgài) is a confident "probably, most likely"; 可能 (kěnéng) is a more neutral "maybe, could be." Both sit before the verb, and both often layer with the 会…的 prediction frame.
他大概在家，这个点儿他一般不出门。
tā dàgài zài jiā, zhège diǎnr tā yìbān bù chūmén
He's probably home — he usually doesn't go out at this hour. (informal) — 大概, a confident 'probably'.
他可能在家，也可能出去了，我也不确定。
tā kěnéng zài jiā, yě kěnéng chūqù le, wǒ yě bú quèdìng
He might be home, or he might have gone out — I'm not sure either. (informal) — 可能 at even odds.
The full workout on 可能 — including its life as a noun (有可能) and the 不可能 / 可能不 negation split — is on the 可能 page.
Lower rungs: 也许 / 说不定 — "perhaps / who knows"
At the bottom you are barely committing. 也许 (yěxǔ) is an open, faintly bookish "perhaps"; 说不定 (shuōbudìng) is a lively, spoken "who knows — it just might," often with a hopeful tilt.
他也许在家，你先打个电话吧。
tā yěxǔ zài jiā, nǐ xiān dǎ ge diànhuà ba
Maybe he's home — try calling first. (neutral)
说不定他在家呢，我们过去看看。
shuōbudìng tā zài jiā ne, wǒmen guòqù kànkan
Who knows, he might be home — let's go over and check. (colloquial) — 说不定, hopeful and spoken.
说不定 gets its own treatment, including why it feels "realer than you'd expect," on the 说不定 page.
Off to the side: 恐怕 — probable and unwelcome
恐怕 (kǒngpà) sits at roughly the "probably" rung but adds a colour no English adverb carries alone: the outcome is likely and regrettable. It is the polite "I'm afraid (that)…" you use to soften bad news. Despite containing 怕 ("fear"), it is not about being scared of anything.
今天恐怕来不及了，我们改天吧。
jīntiān kǒngpà láibují le, wǒmen gǎitiān ba
I'm afraid we won't make it today — let's do another day. (polite) — 恐怕 flags a likely, unwelcome outcome.
Common Mistakes
1. Flattening every guess to 可能. Using the middle rung when you are actually quite sure — or barely sure — wastes the scale.
❌ 灯亮着，门开着，他可能在家。
Under-committed — with the light on and door open you're nearly certain, so 一定/肯定 fits: 他一定在家.
✅ 灯亮着，门开着，他肯定在家。
dēng liàng zhe, mén kāi zhe, tā kěndìng zài jiā
The light's on and the door's open — he's certainly home. — climb to 肯定 when the evidence is strong.
2. Confusing 一定 (certain) with 一定要 (insist). Bare 一定 is a prediction; adding 要 makes it a demand.
❌ 你一定来。
Odd for 'you must come' — this reads as a prediction, 'you'll surely come'; add 要.
✅ 你一定要来。
nǐ yídìng yào lái
You absolutely have to come. — 一定要 for insistence.
3. Using 恐怕 for welcome news. 恐怕 implies the outcome is a shame; for a hopeful "maybe," use 说不定 or 也许.
❌ 恐怕你会中奖。
Wrong colour — 恐怕 makes winning sound like bad news; use 说不定你会中奖.
✅ 说不定你会中奖。
shuōbudìng nǐ huì zhòngjiǎng
Maybe you'll win the prize! — 说不定 for a hopeful chance.
4. Trailing the adverb at the end. Certainty adverbs sit before the verb or lead the clause, never at the end.
❌ 他在家一定。
Incorrect — the adverb precedes the verb: 他一定在家.
✅ 他一定在家。
tā yídìng zài jiā
He's definitely home. — 一定 before the verb.
Key Takeaways
- Chinese grades confidence with a ladder of adverbs; picking the rung tells the listener exactly how sure you are.
- From sure to unsure: 一定/肯定 > 应该 > 大概/可能 > 也许 > 说不定, with 恐怕 at the "probably" rung but flagged as unwelcome.
- Don't default to 可能 for everything — calibrate up to 应该/一定 when the evidence is strong, down to 也许/说不定 when it's thin.
- Watch two boundaries: 一定 (certain) vs 一定要 (insist), and 恐怕 (bad-news probable) vs a hopeful 也许/说不定.
- Layer 吧 for a softened guess and 会…的 to seal a prediction — the adverb sets the rung, the particles fine-tune it.
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- 可能 (Possible / Maybe / Probably)HSK 3 — 可能 (kěnéng) is Chinese's all-purpose mid-scale likelihood word — one form does the work of English 'maybe / possibly / probably' (adverb), 'might' (before a modal), and 'possibility / possible' (noun and adjective): 他可能忘了 'he probably forgot', 有可能 'it's possible', 这不可能 'that's impossible'.
- 说不定 (Maybe / You Never Know)HSK 5 — 说不定 (shuōbudìng) literally means 'can't say for sure' and works as a lively, spoken 'maybe / who knows / it might well be' — often hinting the possibility is realer than you'd expect: 说不定他已经到了 'maybe he's already arrived', 说不定会下雨 'it might well rain'. It leads the clause and leans hopeful.