It’s natural that many writers confuse the similar-looking, sound-alike terms allusion and illusion, as well as the rare elusion, and their verb forms: They’re all related.
These words all stem from the Latin root word ludere, meaning “to play,” which also forms the basis for ludicrous. Meet the other members of this frolicsome family:
Allusion: An allusion is a reference to something, but with a special sense: The reference is implied, or indirect. (The verb form is allude.) If you think of an allusion as coy or playful, the etymology makes sense.
Illusion: An illusion is something misleading or open to misinterpretation. (The Latin term illusio means “mockery.”) Again, the root word is apt if, in this case, you think of an illusion as something that occurs when your mind plays tricks on you.
Elusion: An elusion (from the Latin word for “deception”) is an act of eluding, and “to elude” means “to avoid or evade.” (This term is not to be confused with elision — verb form: elide — which means “to delete or omit,” as in contractions or missing words.)
That’s not all: There’s also collusion (verb form: collude), literally meaning “to play with” and referring to a conspiracy, and delusion (verb form: delude), which means “to trick.” Three related nouns that lack the -sion suffix and look like the other verb forms are prelude (literally, “before play”), interlude (“during play”), and the rare postlude (“after play”). Prelude refers to a performance or action that precedes a more significant event, an interlude is an intermission, and a postlude is a closing piece of a musical or literary composition.
The words include, conclude, exclude, occlude, preclude, and seclude and their noun forms, by the way, are unrelated to the -lude family, stemming from a Latin word meaning “to close.”