illusion

/ɪˈluːʒn इˈलूश़्‌न्‌/ noun

1 [C, U] a false idea, belief or impression निराधार विचार, धारणा या प्रभाव; भ्रम

I have no illusions about the situation—I know it’s serious.

I think Puneet’s under the illusion that he will be the new director.

2 [C] something that your eyes tell you is there or is true but in fact is not (वास्‍तविकता के विपरीत) किसी वस्‍तु की सत्ता होने का आभास; दृष्टिभ्रम

That line looks longer, but in fact they’re the same length. It’s an optical illusion.