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

In fact, many early versions of vaccines, like ones for polio and measles, were tested against unvaccinated groups or a placebo. —Tom Bartlett, The Atlantic, 24 Feb. 2026

In the study, participants treated for six months with the Gossamer drug, called seralutinib, walked 13 meters farther over six minutes compared to participants offered a placebo. —Adam Feuerstein, STAT, 23 Feb. 2026

Before it was released, it was tested on nearly two million children, with some getting the vaccine, and some getting a placebo. —Jon Lapook, CBS News, 22 Feb. 2026

This isn’t a bad thing when asked for or welcome, but everybody is different and one person’s miracle cure might be another person’s placebo. —R. Eric Thomas, Chicago Tribune, 20 Feb. 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)