Meaning

noun

the ability to produce a desired or intended result

In simple words

Efficacy means how well something works and produces the result you want.

Example sentences

  1. The doctors tested the efficacy of the new medicine.
  2. We doubted the efficacy of his unusual plan.
  3. Scientists measured the vaccine's efficacy against the illness.
  4. The efficacy of the treatment surprised everyone.

Synonyms

  • effectiveness
  • potency
  • efficiency
  • usefulness

Antonyms

  • ineffectiveness
  • uselessness
Illustration for the story The Great Hiccup Experiment

The story

The Great Hiccup Experiment

Sora's little brother Kenji had the hiccups. Not ordinary hiccups — enormous ones that made him bounce off his chair like popcorn.

"Right," said Sora, fetching her notebook. "We shall test every cure and record its efficacy. Science demands it."

Efficacy means how well something works and produces the result you want.

Kenji hiccupped so hard his glasses slid down his nose.

Cure number one: drinking water upside down. Kenji tried. Most of the water went up his nose, and the hiccups carried on. Sora wrote: *Efficacy — terrible. Also soggy.*

Cure number two: holding his breath while thinking about jelly. Kenji went pink, then pinker, then let out a hiccup so loud the cat left the room in disgust. Sora sighed and wrote: *Not even slightly efficacious. Cat now cross.*

Cure number three: standing on one leg and singing the alphabet backwards. Kenji got stuck at W, lost his balance, and hiccupped into the fruit bowl.

"This is hopeless," Kenji groaned. "I shall hiccup forever. They'll have to hiccup-proof my school."

Then Mum wandered in. "Kenji," she said calmly, "you left your muddy boots on my clean floor."

Kenji froze. His eyes went wide. He waited for a hiccup.

Nothing came.

"They've gone!" he whispered. "Mum's telling-off voice cured me!"

Sora scribbled furiously: *Mum's voice — one hundred per cent efficacy. Works faster than water, faster than jelly, faster than the alphabet. Quite possibly the most efficacious cure ever recorded.*

Mum raised an eyebrow. "I'm not sure whether to be proud or offended."

"Proud," said Sora, closing her notebook. "You're the best cure in the house."

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