名詞 delusion:

1. (psychology) an erroneous belief that is held in the face of evidence to the contrary
   同義詞：psychotic belief
2. a mistaken or unfounded opinion or idea
   同義詞：hallucination
3. the act of deluding; deception by creating illusory ideas
   同義詞：illusion, head game

1. He labours under the delusion that he's a fine actor.
   他有個錯覺，以為自己是個好演員。
2. Your hope of promotion is a mere delusion.
   你提升的希望只不過是一種幻覺。
3. His arguments sound convincing but they're based on delusion.
   他的論據(jù)聽起來似乎有理，但根本上是欺騙性的。

de.lu.sion

n.（名詞）

The act or process of deluding.
欺騙，騙局：欺騙人的行為或過程
The state of being deluded.
受騙：被欺騙的狀態(tài)
A false belief or opinion:
錯覺，幻覺：虛假的信念或觀點：
例句：
labored under the delusion that success was at hand.
誤以為成功垂手可得而苦惱

Psychiatry A false belief strongly held in spite of invalidating evidence, especially as a symptom of mental illness:
【精神病學】 妄想癥：一種強烈的虛幻的信念，即使有使之無效的證據(jù)也毫不動搖，特指一種精神病癥狀：
例句：
delusions of persecution.
迫害幻想癥

來源：
Middle English delusioun
中古英語 delusioun
from Latin dôlôsiô dôlôsiôn-
源自 拉丁語 dôlôsiô dôlôsiôn-
from dôlôsus [past participle of] dôlôdere [to delude] * see delude
源自 dôlôsus [] dôlôdere的過去分詞 [欺騙，迷惑] *參見 delude

【引伸】
delu.sional
adj.（形容詞）