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.
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.
His head is full of delusions.
He is under the delusion that he is a genius.
Treatment for delusional disorder often takes time.
A simple misunderstanding or mistaken belief. Softer than 妄想.
That's just a misunderstanding.
A mistaken assumption or mix-up. Very common in daily conversation.
I was mistaken in thinking he would come.
Illusion or misperception, often sensory. Can be used metaphorically for a false belief.
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.
Thinking she likes me is just a delusion.
Commonly used for personal fantasies, especially in otaku culture or when describing unrealistic daydreams.
He's always deluding himself about his success.
That's just a fantasy, right?
Daydream or fantasy, often more innocent and imaginative than 妄想.
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.
His ideal was nothing but an illusion.
To indulge in delusions/fantasies. Often used for escapist or obsessive daydreaming.
He spends all day lost in his fantasies.
Self-deception. A formal term, but clearly captures the idea of lying to oneself.
That's nothing but self-deception.
To convince oneself of something convenient. A natural, colloquial way to express wishful thinking.
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.
It's a delusion to think he'll come back.
空想の世界に浸る。
Immerse oneself in a world of fantasy.
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.
Stop living in a fantasy world.