Difference in meaning: illusion vs. delusion

[Annaa]

Illusion and delusion? Is there any difference in meaning?

Thanks in advance.

Anna

[Mister Micawber]

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The Random House Dictionary comments:

An illusion is a false mental image produced by misinterpretation of things that actually exist: 'A mirage is an illusion produced by reflection of light against the sky'.... A delusion is a persistent false belief: A' paranoiac has delusions of persecution'.
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Native English teacher at Mister Micawber's