Illusion (noun)

1. A deceptive appearance or impression.
2. A false idea or belief.
3. Something that is or is likely to be wrongly perceived or interpreted by the senses.

Origin:

Late middle english: via old french from latin illusio(n-), from illudere 'mock, ridicule'. the current sense dates from the late 16th century.

Examples:

1. The city skyline was a beautiful illusion created by lights.
2. The magician's tricks were a clever illusion.
3. He had an illusion that he was the best singer in the world.
4. It was an illusion that he could quit smoking easily.
5. The desert mirage is a classic example of an illusion.