an innocuous or inert medication; given as a pacifier or to the control group in experiments on the efficacy of a drug
"The doctor gave the patient a sugar pill as a placebo to test whether their recovery was due to the new medicine or simply the belief that they were being treated."
(Roman Catholic Church) vespers of the office for the dead
"The medieval monks sang the Placebo during their solemn vespers service honoring the departed faithful."
A dummy medicine containing no active ingredients; an inert treatment.
"The doctor gave him a sugar pill as a placebo to test whether his belief in the cure could heal his pain without any actual medication."
In plain English: A placebo is an inactive substance given to someone as if it were real medicine, often just because they believe it will help them feel better.
"The doctor gave her a placebo tablet to see if she felt better just because she believed it would work."
Usage: A placebo refers to an inactive substance or procedure used in medical trials, not the psychological effect it may produce on patients. Researchers often use placebos as a control group to compare against treatments that contain actual medicinal ingredients.
The word placebo comes from Latin, where it originally meant "I will please." It entered Middle English and later modern usage to describe a treatment given with no therapeutic effect.