Longman Dictionary of Contemporary English homepage

Date: 1700-1800
Language: Latin
Origin: 'I shall please', from placere; PLEASE2

placebo

noun
     
pla‧ce‧bo plural placebos [countable]
1MI a harmless substance given to a sick person instead of medicine, without telling them it is not real. Placebos are often used in tests in which some people take real medicine and others take a placebo, so that doctors can compare the results to see if the real medicine works properly.
2

placebo effect

when someone feels better after taking a placebo, even though it has not had any effect on their body

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