Translation guide
In Japanese, expressing 'delusion' depends on whether you mean a clinical false belief, a mistaken idea, a daydream, or a self-indulgent fantasy. The most common everyday word is 妄想, but it can sound clinical or intense. For casual daydreaming or wishful thinking, other expressions are more natural.
A firmly held false belief despite evidence to the contrary, often associated with mental illness.
The standard term for delusion in psychiatric contexts. Can also be used more broadly for wild fantasies.
彼は被害妄想に苦しんでいる。
He suffers from persecutory delusions.
Delusional disorder, the clinical diagnosis.
妄想障害の治療には時間がかかることが多い。
Treatment for delusional disorder often takes time.
A belief that is wrong or not based on reality, but not necessarily pathological.
An imagined scenario or wishful thinking, often romantic or grandiose.
Believing something because you want it to be true, despite evidence.
妄想 (もうそう) is the most direct translation for 'delusion' and can range from clinical to fanciful. 空想 (くうそう) is a neutral 'daydream' or 'fantasy' without the negative connotation. 幻想 (げんそう) is an 'illusion' or 'fantasy' often used in artistic or literary contexts, implying something ephemeral and beautiful.
彼の頭の中は妄想でいっぱいだ。
His head is full of delusions.
彼は自分が天才だという妄想に取り憑かれている。
He is under the delusion that he is a genius.
A simple misunderstanding or mistaken belief. Softer than 妄想.
それはただの思い違いだよ。
That's just a misunderstanding.
A mistaken assumption or mix-up. Very common in daily conversation.
彼が来ると思ったのは勘違いだった。
I was mistaken in thinking he would come.
Illusion or misperception, often sensory. Can be used metaphorically for a false belief.
それは単なる錯覚に過ぎない。
It's nothing more than an illusion.
Can be used hyperbolically for a wild or unrealistic belief, but may sound overly dramatic.
Using 妄想 for a simple mistake can sound like you're accusing someone of being crazy.
彼女が僕を好きだなんて、ただの妄想だ。
Thinking she likes me is just a delusion.
Commonly used for personal fantasies, especially in otaku culture or when describing unrealistic daydreams.
彼はいつも自分の成功を妄想している。
He's always deluding himself about his success.
そんなのただの妄想でしょ。
That's just a fantasy, right?
Daydream or fantasy, often more innocent and imaginative than 妄想.
子供の頃はよく空想にふけったものだ。
I used to indulge in daydreams when I was a child.
Illusion or fantasy, often with a literary or artistic nuance. Can imply something beautiful but unreal.
彼の理想は幻想に過ぎなかった。
His ideal was nothing but an illusion.
To indulge in delusions/fantasies. Often used for escapist or obsessive daydreaming.
彼は一日中妄想にふけっている。
He spends all day lost in his fantasies.
Self-deception. A formal term, but clearly captures the idea of lying to oneself.
それは自己欺瞞に過ぎない。
That's nothing but self-deception.
To convince oneself of something convenient. A natural, colloquial way to express wishful thinking.
彼女は都合のいいように思い込んでいるだけだ。
She's just deluding herself into believing what's convenient.
Can be used, but often implies a more severe disconnect from reality.
May sound too strong for simple wishful thinking.
彼が戻ってくるなんて妄想だ。
It's a delusion to think he'll come back.
Immerse oneself in a world of fantasy.
それは幻想に過ぎなかった。
It was merely an illusion.
While 妄想 is the direct equivalent, using it for minor misunderstandings or innocent daydreams can sound overly dramatic or clinical. In casual conversation, 勘違い or 思い違い are safer for simple mistakes, and 空想 is better for harmless fantasies.
It's just a delusion; she doesn't really love you.
思い込み (belief/assumption) is often more natural than 妄想 for romantic delusions.
妄想の世界に生きるのはやめろ。
Stop living in a fantasy world.