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

Another large-scale analysis of 50 studies presented this fall at the American Neurological Association annual meeting found that the risk of Alzheimer’s was up to 32% lower among women who started HRT within five years of menopause than in those who received a placebo or no treatment. —Akshay Syal, NBC news, 27 Nov. 2025

In a 2017 study, adults who took diosgenin extract daily for 12 weeks scored better on cognitive tests (including memory, language, and attention) than a placebo group. —Mark Gurarie, Health, 24 Nov. 2025

The two-year study included more than 3,800 people with mild cognitive impairment or mild dementia due to Alzheimer’s, half of whom were randomly assigned to take a semaglutide pill every day, and half of whom took placebo. —Alice Park, Time, 24 Nov. 2025

In two Phase 3 trials of more than 3,800 adults receiving standard care for Alzheimer’s, the company evaluated whether an older pill form of semaglutide worked better than a placebo. —Jamie Gumbrecht, CNN Money, 24 Nov. 2025

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)