illusion“幻覺，錯覺”
be under no illusion about sth.對某事不存幻想。
A mirage is an optical illusion.
海市蜃樓是一種視錯覺。
I thought I saw a ghost but it was just an optical illusion.
我以為我看見鬼了，其實只是一種幻覺。
I was under the illusion that he was honest until he was caught stealing some money.
他偷錢當場被人抓住，在此之前我一直誤以為他是個老實人。
He cherished the illusion that she loved him, but he was wrong.
他抱有她愛他的幻覺，但他錯了。
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delusion“欺騙，迷惑”
delusion是某人或其他人一直堅持的錯誤信念，儘管這種信念和事實不符。
He suffers from the delusion that he"s attractive to women.他糊里糊塗地認為自己對女人很有吸引力。
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。
Your hope of promotion is a mere delusion.
你提升的希望只不過是一種幻覺。
His arguments sound convincing but they"re based on delusion.
他的論據聽起來似乎有理，但根本上是欺騙性的。
illusion“幻覺，錯覺”
be under no illusion about sth.對某事不存幻想。
A mirage is an optical illusion.
海市蜃樓是一種視錯覺。
I thought I saw a ghost but it was just an optical illusion.
我以為我看見鬼了，其實只是一種幻覺。
I was under the illusion that he was honest until he was caught stealing some money.
他偷錢當場被人抓住，在此之前我一直誤以為他是個老實人。
He cherished the illusion that she loved him, but he was wrong.
他抱有她愛他的幻覺，但他錯了。
=============================================
delusion“欺騙，迷惑”
delusion是某人或其他人一直堅持的錯誤信念，儘管這種信念和事實不符。
He suffers from the delusion that he"s attractive to women.他糊里糊塗地認為自己對女人很有吸引力。
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。
Your hope of promotion is a mere delusion.
你提升的希望只不過是一種幻覺。
His arguments sound convincing but they"re based on delusion.
他的論據聽起來似乎有理，但根本上是欺騙性的。