〜かもしれない is how Japanese says "might, maybe, perhaps" — and it means it. This is the low-confidence end of the whole conjecture spectrum: the speaker sees a real possibility but is equally ready for the opposite. English "might" and "maybe" hide how tentative they are, so learners reach for かもしれない when they actually feel fairly sure — and end up sounding far more doubtful than they meant. This page fixes the confidence calibration, drills the attachment (which trips people up after nouns), and places かもしれない on the certainty scale against でしょう, はず, and にちがいない.
What it literally says: "it can't be ruled out"
かもしれない parses transparently, and the parts explain the meaning. か is the question particle ("whether…?"); も is "even"; しれない is the negative potential of 知る, "cannot be known." Put together: "even whether X is so cannot be known" — i.e. "it can't be ruled out that X." That is why かもしれない commits you to nothing: it merely says the possibility is open. It does not lean toward X being true; it just declines to close the door. Hold onto that literal reading and you will never overstate it.
明日は雪になるかもしれない。
ashita wa yuki ni naru kamoshirenai
It might turn to snow tomorrow.
道が混んでいるかもしれませんから、早めに出ましょう。
michi ga konde iru kamoshiremasen kara, hayame ni demashō
The roads might be congested, so let's leave a bit early. (polite)
彼、もう帰ったかも。
kare, mō kaetta kamo
He might've already gone home. (casual, clipped)
How it attaches
かもしれない follows the plain form of verbs and い-adjectives, and the bare noun or な-adjective stem — with no だ. This last point is where English speakers stumble, so make it a rule: after a noun or な-adjective, drop だ and attach directly.
| Base type | Example | Meaning |
|---|---|---|
| Verb (plain) | 降るかもしれない | might rain |
| Verb (negative) | 間に合わないかもしれない | might not make it |
| Verb (past) | 帰ったかもしれない | might have gone home |
| い-adjective | 高いかもしれない | might be expensive |
| な-adjective (drop だ) | 静かかもしれない | might be quiet |
| Noun (drop だ) | 学生かもしれない | might be a student |
財布、家に忘れたかもしれない。
saifu, ie ni wasureta kamoshirenai
I might've left my wallet at home.
彼女はまだ学生かもしれない。
kanojo wa mada gakusei kamoshirenai
She might still be a student.
この薬は眠くなるかもしれませんので、運転は控えてください。
kono kusuri wa nemuku naru kamoshiremasen node, unten wa hikaete kudasai
This medicine may make you drowsy, so please refrain from driving. (polite / official)
Register: かもしれない, かもしれません, かも
The form flexes across three politeness levels, and choosing the wrong one is a register slip:
- かもしれない — plain, neutral; fine in writing and casual speech.
- かもしれません — polite; the default in conversation with strangers, service situations, and business.
- かも — a casual clip of the whole thing, very common in speech and texting: 行くかも ("might go"), だめかも ("might be no good"). Strongly (informal) — do not use it in polite or written contexts.
There is also かもしれん (a blunt, masculine / (regional) contraction, common in western Japan and rough male speech) and, in formal writing, the option to spell out possibility with 〜可能性がある ("there is a possibility that…"). But the three above cover almost everything.
今から行っても間に合わないかも。
ima kara itte mo maniawanai kamo
Even if we leave now, we might not make it. (casual)
ひょっとしたら、私が間違っているのかもしれない。
hyotto shitara, watashi ga machigatte iru no kamoshirenai
Maybe I'm the one who's wrong.
The adverb ひょっとしたら (also もしかしたら / もしかすると) pairs naturally with かもしれない, front-loading the "maybe" and reinforcing the tentativeness. It is the idiomatic way to flag "just possibly…" before the clause.
Where it sits on the certainty scale
This is the calibration that matters most. Japanese conjecture forms line up by confidence, and かもしれない sits near the bottom — roughly a coin-flip or less, genuine doubt with no lean. It is well below the forms learners often confuse it with:
| Confidence | Form | Feel |
|---|---|---|
| lowest | 〜かもしれない | "might" — could go either way |
| ↓ | 〜だろう／でしょう | "probably" — a real lean toward yes |
| ↓ | 〜はず | "supposed to be" — grounded expectation |
| highest | 〜にちがいない | "surely, no doubt" — near-certainty |
The practical upshot: if you feel fairly sure, かもしれない undersells you. Reaching for it commits you to real uncertainty. When an English speaker means "he'll probably come," the right tool is 〜だろう／でしょう or 〜と思う, not かもしれない — 来るかもしれない says only "he might come, might not." When you have a solid basis for expecting something, use 〜はず; when you are all but certain, 〜にちがいない. The full lineup is on the probability spectrum page.
English "might/maybe" is one modal — かもしれない is one clause-ender
English scatters possibility across modals (might, may, could) and adverbs (maybe, perhaps, possibly), and it can stack them ("it might possibly…"). Japanese folds all of that into one clause-final expression. There is no separate modal verb hovering before the main verb; the whole idea rides on the end of the plain-form clause. This is why the attachment is so mechanical — you build a complete plain sentence, then bolt かもしれない on. It is also why the negative lives inside the clause (間に合わないかもしれない, "might not make it"), never on かもしれない itself.
明日は雨かもしれないし、傘を持って行こう。
ashita wa ame kamoshirenai shi, kasa o motte ikō
It might rain tomorrow, so let's take an umbrella.
高いかもしれませんが、質はいいですよ。
takai kamoshiremasen ga, shitsu wa ii desu yo
It might be expensive, but the quality is good. (polite, concessive)
The 〜かもしれないが / 〜かもしれないけど pattern ("it may be X, but…") is a soft, common way to concede a point before pushing back — a natural home for かもしれない's built-in hedge.
Common Mistakes
1. Inserting だ after a noun or な-adjective. Attach directly to the bare word.
❌ 彼は学生だかもしれない。
kare wa gakusei da kamoshirenai
Wrong — drop the だ: 学生かもしれない.
✅ 彼は学生かもしれない。
kare wa gakusei kamoshirenai
He might be a student.
2. Using かもしれない when you mean "probably." It's genuine 50/50; too weak for a real lean.
❌ 彼はきっと来るかもしれない。
kare wa kitto kuru kamoshirenai
Contradictory — きっと ('surely') clashes with the ~coin-flip かもしれない.
✅ 彼はきっと来るでしょう。／来ると思う。
kare wa kitto kuru deshō / kuru to omou
He'll surely come. / I think he'll come.
3. Using casual かも in a formal setting. In polite or written contexts, spell it out.
❌ 会議が延期になるかも、とメールしておきました。
kaigi ga enki ni naru kamo, to mēru shite okimashita
Too casual for a business note — use 〜かもしれません.
✅ 会議が延期になるかもしれない、とメールしておきました。
kaigi ga enki ni naru kamoshirenai, to mēru shite okimashita
I emailed to say the meeting might be postponed.
4. Trying to make an affirmative "かもしれる." しれない is a fossilized negative — there is no ×かもしれる.
❌ 雨が降るかもしれる。
ame ga furu kamoshireru
Not a word — the expression is frozen as かもしれない (only the whole form varies for politeness).
✅ 雨が降るかもしれない。
ame ga furu kamoshirenai
It might rain.
5. Attaching to the ます-form or て-form. Use the plain form.
❌ 彼は来ますかもしれない。
kare wa kimasu kamoshirenai
Wrong — plain form: 来るかもしれない.
✅ 彼は来るかもしれない。
kare wa kuru kamoshirenai
He might come.
Key Takeaways
- 〜かもしれない = "might / maybe", genuine ~coin-flip possibility with no commitment — literally "it can't be ruled out."
- Attaches to the plain form and to bare nouns / な-stems (no だ); the negative goes inside the clause.
- Register: かもしれない (neutral) / かもしれません (polite) / かも (casual clip).
- It sits low on the certainty scale — below でしょう ("probably"), はず ("supposed to"), and にちがいない ("surely"). If you're fairly sure, reach for one of those instead.
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- でしょう / だろう: ConjectureN4 — でしょう/だろう as the everyday 'probably' of the modality system — a confident guess that sits above かもしれない and below はず, and, with a rising tone, doubles as the tag 'isn't it?'
- 〜はず: Expectation ('supposed to')N3 — How Japanese states a logical expectation drawn from known facts — 来るはずだ 'should be coming' — plus はずがない ('couldn't possibly') and the regretful はずだった ('was supposed to, but…').
- 〜にちがいない: Conviction ('must be')N2 — 〜にちがいない ('must be / surely / no doubt') — the top of the certainty scale, expressing the speaker's confident deduction from evidence — how it attaches, why it's the inferential 'must' and never the obligation 'must', and how it differs from objective はず.
- The Probability SpectrumN3 — The full Japanese confidence ladder — かもしれない < でしょう < はず < にちがいない — organized by two axes (how sure you are, and why), so you stop guessing at 'maybe/probably/should/must' by feel.