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

By week eight, 31% of those treated with PP405 had a 20% increase in hair density, compared to 0% in the placebo group, according to a Pelage press release. —The Week Uk, TheWeek, 27 Mar. 2026

Still, the company said the shot reduced the rate of infection by more than 70% in people who received the vaccine versus placebo, efficacy the company thinks is strong enough to take to regulators. —Angelica Peebles, CNBC, 23 Mar. 2026

The Dog Aging Project is now conducting a larger clinical trial funded, in part, by the National Institutes of Health, giving hundreds of dogs -- including Murphy -- either a placebo or rapamycin to see if the drug can extend life. —Anderson Cooper, CBS News, 22 Mar. 2026

No one taking placebo quit the trial early. —Emily Kay Votruba, EverydayHealth.com, 20 Mar. 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)