placebo effect

American

[pluh-see-boh] / pləˈsi boʊ /

noun

a reaction to a placebo manifested by a lessening of symptoms or the production of anticipated side effects.

placebo effect British

noun

med a positive therapeutic effect claimed by a patient after receiving a placebo believed by him to be an active drug See control group

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of placebo effect

First recorded in 1945–50

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Even those who swear by the broccoli concoction say they can’t be sure that they are benefiting from anything other than a placebo effect.

From The Wall Street Journal • Feb. 12, 2026

The placebo effect might also be at work.

From The Wall Street Journal • Dec. 29, 2025

“The placebo effect can also be very powerful, especially for treatments that require significant effort and cost.”

From Los Angeles Times • Sep. 12, 2025

He warned a pineal cyst should only be removed in extremely rare circumstances, and believes the operations' successful results could be explained by the "placebo effect".

From BBC • Dec. 4, 2024

It must have been a placebo effect, but it was a great placebo effect.

From "It’s Kind of a Funny Story" by Ned Vizzini

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023