illusion

Everyday

1. Something that seems real or true but is not: a trick of the eyes or the mind. tree →
2. An optical illusion: a picture that tricks your eyes, like lines that look different lengths but are the same. tree →
3. A false idea or belief: «He was under the illusion that school was cancelled». tree →
4. A magic trick on a stage. tree →

In the lessons

In science: optical illusions show that the brain guesses what we see, and it can be fooled; a mirage in the desert is a real illusion of water. In lessons about tricks and fake news: things can look true but be illusions, so check. Phrases: «optical illusion», «under the illusion that», «the illusion of», «magic illusion».

Examples

• The two lines look different, but it's an optical illusion — they're the same length. tree →
• The magician's illusion made the rabbit vanish. tree →
• A mirage is an illusion of water in the hot desert. tree →
• He was under the illusion that he would win easily. tree →
• The mirror gives the illusion of a bigger room. tree →
• Measure the lines with a ruler to beat the illusion. tree →

Note

«An illusion» (it starts with a vowel sound). Do not confuse with «allusion» (a hint or mention of something) or «delusion» (a strong false belief, often a sign of illness). Countable.