"Don’t do it!" said Mr. Crunches looking about, as if he rather expected to see the loaf disappear under the efficacy of his wife’s petitions.
The devoutest person could have rendered no greater homage to the efficacy of an honest prayer than he did in this distrust of his wife.
The officiating undertakers made some protest against these changes in the ceremonies; but, the river being alarmingly near, and several voices remarking on the efficacy of cold immersion in bringing refractory members of the profession to reason, the protest was faint and brief.
There are no more uses of "efficacy" in the book.
Show samples from other sources
The doctor weighed the efficacy of each treatment against potential side-effects.
They held hearings to investigate concerns about the safety and efficacy of the vaccine.