Allusion vs. Illusion The similar spellings and pronunciations of allusion and illusion can cause even seasoned writers to second-guess their choice of words. Today we will examine and clarify the differences between these two terms, so you won’t be fooled again by their deceptive likeness. What do allusion and illusion mean? An allusion is a reference, direct or implied, to something or someone. Allusions are often found in books, songs, TV shows, and movies. For instance, the title of Aldous Huxley’s classic novel Brave New World is an allusion to a work by William Shakespeare; the phrase brave new world is spoken by Prospero’s daughter, Miranda, in The Tempest: “How beauteous mankind is! O brave new world, That has such people in ’t!“ An illusion, on the other hand, is something that deceives the mind or senses by creating a false impression of reality. Illusions are often (though not always) related to visual perception, as in “optical illusion.” A mirage, such as the phenomenon of perceiving a sea of water in a desert, is a type of illusion. A common root word Allusion and illusion are both related to the Latin term lūdere meaning “to play,” along with their linguistic cousin delusion. Keep in mind the prefix de-, denoting privation or negation, provides a hint to the more serious contexts in which this term is sometimes used. A delusion is a false belief or opinion. In the context of mental health, a delusion can be defined as a fixed false belief that is resistant to reason or confrontation with actual fact, as in “paranoid delusion.” To keep them straight, try associating the beginning I in illusion with an eye, relating the term to optical illusions.