placebo

inactive treatment that may still produce a perceived benefit

Root

plac: please, soothe, settle into calm

Other words with the plac root

complacent: self-satisfied and unaware of risk
complaisant: eager to please or agree with others
implacable: unable to be appeased
placate: to calm someone down
placatory: intended to soothe, calm, or appease
placid: calm, peaceful, and undisturbed
placidity: calmness or peaceful stillness

Placebo keeps the pleasing/reassuring thread: sometimes expectation changes what a patient feels.

The trial compared the new pill with a placebo to separate chemistry from expectation.

Placebo is the strange medical cousin of plac. It does not mean fake cure in a careless way; in trials, it helps separate the chemical effect from the power of expectation, reassurance, and being treated.