An optical illusion–I see movement and three dimensions. Perhaps I am deluded.
Here are a few words that look as if they might be related, but they have different meanings:
ILLUSION: 1) A false belief or idea. 2) Something that is perceived incorrectly, such as an optical illusion. For example, at times the moon appears to be enormous, but, in fact, it doesn’t change its size. For a multitude of optical illusions, google the art of MC Escher.
ALLUSION: A reference to something without specifically mentioning it. For example, many literary works contain allusions to Shakespeare’s plays.
DELUSION: An idea firmly held but not founded in fact. Paranoid thought can involve many delusions.