Illusion (noun)
An illusion is something that looks real but is not — a false appearance or misleading perception of reality (भ्रम/ माया)
The magician created an illusion of a floating man.
The mirror created the illusion of a larger space.
The desert travelers saw an illusion of water — it was just a mirage.
Delusion (noun)
A delusion is a false belief that a person firmly holds, even when it’s clearly not true (भ्रांति/ वहम)
He suffers from the delusion that he is a king.
He lives under the delusion that he can control everything.
Many dictators suffer from the delusion of greatness.
Click to know the difference between Illusion, Delusion and Hallucination