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

Similar clinical studies showed that nearly 7 out of 10 people who took TEPEZZA saw improvements in double vision, compared to 3 out of 10 who took placebo. —Emily Cegielski, Flow Space, 6 May 2026

With so many products on the market, knowing what each formula actually delivers — and what dietitians and reviewers say about them — can make the difference between an effective hydration habit and a sugary placebo. —Sacbee.com, 6 May 2026

What New Research Says About Caffeine and Sleep A 2025 study published in Communications Biology took the question deeper, using EEG recordings from 40 healthy adults who completed both a 200 mg caffeine condition and a placebo condition. —Samantha Agate, Miami Herald, 6 May 2026

That second issue stemmed from the trial setup, which didn’t have a control group receiving a placebo instead of RP1. —K. R. Callaway, Scientific American, 2 May 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)