Translation guide
Ways to express lack of knowledge, unawareness, or ignorance in Japanese, organized by what kind of 'not knowing' you mean.
You don't know a fact, answer, or piece of information.
The most direct and common way to say you don't know something. Use with a noun or noun phrase.
そのニュースを知らない。
I don't know that news.
I don't know his phone number.
General 'I don't know' or 'I don't understand'. More casual and versatile than 知らない. Can also imply you haven't figured something out.
答えがわからない。
I don't know the answer.
何が起こったのかわからない。
I don't know what happened.
Polite form of 知らない. Use in formal situations or with strangers.
すみません、知りません。
Sorry, I don't know.
Polite form of わからない. Safe for most polite contexts.
申し訳ありませんが、わかりません。
I'm sorry, but I don't know.
You were not aware something happened or existed.
Expresses that you didn't notice or realize something. Often used for past unawareness.
彼が来ていたことに気づいていなかった。
I didn't realize he had come.
Past tense of 知らない, meaning you didn't know about something before (but maybe you do now).
その問題を知らなかった。
I wasn't aware of that problem.
Casual 'I didn't know'. Often used when you just learned something surprising.
え、そうだったの？知らなかった！
Oh, really? I didn't know!
You lack knowledge in a certain field or are generally uninformed.
Means 'to be ignorant'. Can sound harsh if used about others. Often used in self-deprecation.
私はその分野については無知です。
I am ignorant about that field.
Literally 'have no knowledge'. Neutral way to say you lack expertise.
法律の知識がないので、専門家に相談します。
I don't have legal knowledge, so I'll consult an expert.
Emphatic 'I don't know anything'. Can be used when you feel completely clueless.
私は何も知らない。
I don't know anything.
You act as if you don't know something, often deliberately.
To pretend not to know. Common in everyday speech.
彼は知らないふりをした。
He pretended not to know.
To play dumb, feign ignorance. Often used when someone is being evasive.
とぼけないで、本当のことを言って。
Don't play dumb, tell me the truth.
To feign innocence, especially when guilty. Slightly old-fashioned or dramatic.
知らない means you lack information or have never encountered something. わからない means you don't understand or can't figure something out. In many casual situations they overlap, but わからない is softer and more common when you're unsure.
彼の住所を知らない。
I don't know his address. (I never learned it.)
この問題がわからない。
I don't understand this problem. (I can't solve it.)
English 'not knowing' as a gerund doesn't directly map to a single Japanese noun. Use verb phrases like 知らないこと or 無知 depending on context. Don't try to nominalize 知らない as a standalone noun without こと or の.
彼は白を切って、何も知らないと言った。
He feigned innocence and said he knew nothing.