Translation guide
How to express that an action or outcome was not intended, covering accidents, unconscious actions, and lack of intent.
The speaker did something by mistake or without meaning to.
Attach to the te-form of a verb to express that an action happened unintentionally, often with a sense of regret. 〜ちゃう is the casual contraction.
ケーキを全部食べてしまった。
I accidentally ate all the cake.
The speaker did something without being aware of it, but not necessarily a mistake.
Adverb meaning 'unconsciously' or 'without realizing'. Used for actions done without conscious thought.
無意識に髪を触っていた。
I was unconsciously touching my hair.
Stating that something was not done on purpose, often in formal or explanatory contexts.
Formal phrase meaning 'not intentional'. Used in serious situations to deny intent.
それは故意ではありませんでした。
That was unintentional.
〜てしまう is a grammatical pattern that adds the nuance of unintentional action to any verb. うっかり emphasizes carelessness, while つい implies acting against one's better judgment or impulse. They are often combined: うっかり〜てしまう, つい〜てしまう.
うっかり秘密を話してしまった。
I carelessly told the secret.
つい秘密を話してしまった。
I ended up telling the secret (even though I knew I shouldn't).
English 'unintentional' is often an adjective, but Japanese expresses this concept more naturally through adverbs and verb endings. Avoid literal translations like 意図的でない in casual speech; use the patterns above instead.
I dropped my wallet (by accident).
An adverb meaning 'carelessly' or 'inadvertently'. Often used with 〜てしまう to emphasize the accidental nature.
うっかり約束を忘れてしまった。
I carelessly forgot the appointment.
うっかり電車を乗り過ごした。
I accidentally missed my stop.
Adverb meaning 'without thinking' or 'in spite of oneself', used for actions done impulsively or against one's better judgment.
つい食べ過ぎてしまった。
I ended up eating too much without meaning to.
つい秘密を話してしまった。
I unintentionally blurted out the secret.
Adverb meaning 'involuntarily' or 'without thinking', used for spontaneous reactions.
思わず笑ってしまった。
I laughed unintentionally.
思わず叫んでしまった。
I screamed without meaning to.
I was unintentionally humming the same song.
Adverb meaning 'without knowing' or 'unconsciously', often for gradual, unnoticed actions.
知らず知らずのうちに、悪い癖がついていた。
Unintentionally, I had picked up a bad habit.
Adverb meaning 'casually' or 'without much thought', often for actions done unintentionally but without negative connotation.
何気なく言った言葉が彼を傷つけた。
A remark I made unintentionally hurt him.
Casual phrase meaning 'it wasn't on purpose'. Common in everyday speech.
わざとじゃないよ！
It was unintentional! / I didn't do it on purpose!
Noun/adjective meaning 'unintentional' or 'against one's will', often used in formal writing.
不本意な結果に終わった。
It ended in an unintentional result.