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 the analysis, vitamin D supplementation increased the likelihood of returning from prediabetes to normal blood sugar levels by 27% compared with placebo. —Fran Kritz, Verywell Health, 8 Jan. 2026

In comparison, nearly two-thirds of people who took a placebo still experienced vomiting. —Emily Kay Votruba, EverydayHealth.com, 8 Jan. 2026

Observational studies can never prove benefits, which is why studies in which people are randomly assigned to drugs or placebos are so important. —Patricia Bencivenga, STAT, 8 Jan. 2026

Eli Lilly’s orforglipron showed 11% weight loss over 72 weeks on its highest dose, compared with 2% for the placebo group. —Tami Luhby, CNN Money, 6 Jan. 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)