Translation guide
The English modal verb 'cannot' expresses impossibility, inability, or prohibition. In Japanese, these meanings are conveyed through verb conjugations, negative potential forms, and set expressions. The choice depends on whether you mean lack of ability, external impossibility, or a rule-based prohibition.
Expressing that someone is unable to do something due to lack of skill, physical inability, or circumstances.
The most common way to say 'cannot do' is to use the negative potential form of a verb. For ru-verbs, replace 〜る with 〜られない; for u-verbs, change the final -u to -e and add ない; for irregular verbs, する becomes できない and くる becomes こられない.
私は漢字が読めない。
I cannot read kanji.
彼は泳げない。
He cannot swim.
このパソコンは使えない。
I cannot use this computer.
A more formal or written alternative to the potential negative form. It literally means 'the thing of doing is not possible'.
彼は納豆を食べることができない。
He cannot eat natto.
私は車を運転することができない。
I cannot drive a car.
Used when you cannot do something due to social obligation, moral reasons, or a sense of duty, not just lack of ability. It implies 'it's not that I physically can't, but I shouldn't/mustn't'.
約束したから、行かないわけにはいかない。
I promised, so I cannot not go. (I have to go.)
Expressing that something is impossible or cannot happen due to external circumstances, rules, or logic.
The same negative potential form can also express impossibility. Context distinguishes it from inability.
このドアは開けられない。
This door cannot be opened.
明日は来られない。
I cannot come tomorrow.
Similar to ことができない, but often emphasizes the impossibility of the action itself, sometimes with a nuance of 'it's not that I can't do it at all, but under these circumstances I can't'.
今すぐ返事をすることはできない。
I cannot reply right now.
A noun/adjective meaning 'impossible', 'unreasonable', or 'cannot be done'. Often used in casual speech.
それは無理だよ。
That's impossible. / You can't do that.
Expresses strong conviction that something cannot be true or cannot happen based on logic or evidence. 'There's no way that...'
彼がそんなことを言うはずがない。
He cannot have said such a thing. (There's no way he said that.)
Expressing that something is not permitted or forbidden.
The standard way to say 'must not' or 'cannot (because it's not allowed)'. In casual speech, ては becomes ちゃ (or じゃ for 〜では).
ここで写真を撮ってはいけない。
You cannot take photos here. (It's not allowed.)
食べちゃだめ！
You can't eat that! (Don't eat it!)
A formal, written expression meaning 'is not permitted'. Often used in rules or official statements.
ここで喫煙することは許されない。
Smoking is not permitted here.
An archaic/literary form meaning 'must not', seen on old signs or in formal writing. Not used in modern conversation.
立ち入るべからず。
Do not enter. (You cannot enter.)
Expressing that one cannot help doing something or cannot avoid a situation.
Double negative meaning 'cannot not do', i.e., 'must do' or 'have no choice but to do'. It expresses obligation or inevitability.
行かないわけにはいかない。
I cannot not go. (I have to go.)
Means 'cannot afford to do' or 'cannot be doing something' due to urgency or emotional state. Often used with verbs like 泣く, 笑う, 黙る.
泣いてはいられない。
I cannot be crying. (I don't have time to cry.)
Means 'cannot help but do', expressing an uncontrollable urge or natural reaction.
笑わないではいられなかった。
I couldn't help but laugh.
The potential negative form (e.g., 読めない) is more common in everyday speech. ことができない is slightly more formal and often used in writing or polite speech. Both are correct for inability/impossibility.
私は泳げない。
I cannot swim. (casual)
私は泳ぐことができません。
I cannot swim. (polite/formal)
できない means 'cannot do' (lack of ability or possibility). してはいけない means 'must not do' (prohibition). Using the wrong one can change the meaning significantly.
一人で運ぶのは無理です。
It's impossible to carry it alone.