illusion

Etymology

From Old French illusion, from Latin illūsiō, from illūdere, from in- (“at, upon”) + lūdere (“to play, mock, trick”). Displaced native Old English dwimmer.

noun

1. (countable) Anything that seems to be something that it is not.
   We saw what looked like a tiger among the trees, but it was an illusion caused by the shadows of the branches.
   Using artificial additives, scientists can create the illusion of fruit flavours in food.
   You realize the sun don't go down it's just an illusion caused by the world spinning round. 2002, “Do You Realize??”, performed by The Flaming Lips
2. (countable) A misapprehension; a belief in something that is in fact not true.
   Jane has this illusion that John is in love with her.
3. (countable) A magician’s trick.
4. (uncountable) The state of being deceived or misled.