placebo

noun

pla·​ce·​bo plə-ˈsē-(ˌ)bō 

plural placebos

1

a

: a usually pharmacologically inert preparation prescribed more for the mental relief of the patient than for its actual effect on a disorder

b

: an inert or innocuous substance used especially in controlled experiments testing the efficacy of another substance (such as a drug)

2

: something tending to soothe

Did you know?

Doctors doing research on new treatments for disease often give one group a placebo while a second group takes the new medication. Since those in the placebo group usually believe they're getting the real thing, their own hopeful attitude may bring about improvement in their condition. Thus, for the real drug to be considered effective, it must produce even better results than the placebo. Placebos have another use as well. A doctor who suspects that a patient's physical symptoms are psychologically produced may prescribe a placebo in the hope that mentally produced symptoms can also be mentally cured.

Examples of placebo in a Sentence

Recent Examples on the Web

The thresholds described how much an individual patient’s condition had worsened, a company employee told me; they couldn’t be used to judge the average difference between patients receiving a drug and those receiving a placebo. — Manvir Singh, New Yorker, 2 Nov. 2026

Participants received once-weekly injections of retatrutide at doses of 4, 9 or 12 milligrams, or a placebo, and were followed for 80 weeks. — Angelica Stabile, FOXNews.com, 28 Oct. 2026

Acupressure wristbands for motion sickness do not outperform placebos. — Andrés Henao, The Conversation, 27 Oct. 2026

Participants were randomly assigned to receive either the vaccine with pembrolizumab or placebo injections alongside the immune treatment. — Mike McRae 25, New Atlas, 26 Oct. 2026

Word History

Etymology

Latin, I shall please

First Known Use

1785, in the meaning defined at sense 1a

Phrases Containing placebo

• placebo effect

Kids Definition

placebo

noun

pla·​ce·​bo plə-ˈsē-bō 

plural placebos

1

: a medicine that usually has no effect on a disease and is prescribed by a doctor for the mental relief it offers a patient

2

something that is meant to soothe

Etymology

from Latin placebo "I shall please"

Medical Definition

placebo

noun

pla·​ce·​bo plə-ˈsē-(ˌ)bō 

plural placebos

1

: a usually pharmacologically inert preparation prescribed more for the mental relief of the patient than for its actual effect on a disorder

2

: an inert or innocuous substance used especially in controlled experiments testing the efficacy of another substance (as a drug)