“Allusion” and “illusion” are both fairly rare words. They also sound similar, making it is easy to confuse them if you’ve never seen them written down. But these terms have very different meanings, so make sure your work is error free by checking out our guide to how they should be used.
Allusion (Indirect Reference)
An “allusion” is an indirect reference to something. For example, the title of David Foster Wallace’s novel Infinite Jest is taken from a line in Hamlet. This is an “allusion” to Shakespeare – rather than a direct reference – because Wallace does not mention Shakespeare or Hamlet in the novel.
And while “allusion” is a noun, the verb form of this word is “allude”:
The title of the novel alludes to Act 5, Scene 1 of Hamlet.
Again, the key here is the idea of referencing something indirectly.
Illusion (Mistaken Perception or Belief)
The word “illusion” usually refers to a mistaken sense perception, such as a mirage. As such, we could say something like:
He saw the hazy outline of an oasis, but he knew it was an illusion.
Find this useful?
Subscribe to our newsletter and get writing tips from our editors straight to your inbox.
This idea of seeing or sensing something that isn’t really there is also why we say magic tricks are “illusions,” as well as why we call trick images optical illusions. But we can also use “illusion” to describe a false belief:
I was laboring under an illusion to think I could run a marathon.
Here, “laboring under an illusion” means acting on a mistaken belief.
Summary: Allusion or Illusion
These words have many letters in common, but they differ in meaning:
An allusion is an indirect reference to something.
An illusion is a mistaken sense perception or belief.
One trick to remembering this difference is the phrase “Optical illusions will make you ill.” This can remind you that “illusion” starts will an “i,” like the word “ill.” But if you’d like to make extra sure your writing is always error free, you can always ask a proofreader.