1.
delusion, delusional thinking (clinical)
Fixed false beliefs held despite evidence to the contrary, used in psychiatric contexts.
被害妄想に悩まされている。
They are troubled by paranoid delusions.
2.
fantasy, daydream, wild imagination
Fanciful or unrealistic thoughts or imaginings, often used playfully.
また妄想が始まった。
There they go with their fantasies again.
彼女は妄想の世界に浸っている。
She's immersed in her fantasy world.
妄想を膨らませる。
Let one's imagination run wild.
FORMATION: 妄 (reckless/wild) + 想 (thought).
COMMON TYPES (Sense 1):
- 被害妄想 (paranoid delusion, persecution complex)
- 誇大妄想 (delusions of grandeur)
- 関係妄想 (delusion of reference)
CAUSAL USAGE (Sense 2):
In everyday speech, 妄想 is often used lightheartedly to describe daydreaming or unrealistic hopes, especially in otaku and internet culture.
COMMON COLLOCATIONS:
- 妄想する (to fantasize)
- 妄想を膨らませる (let imagination run wild)
- 妄想癖 (tendency to fantasize)