The court depends on its public legitimacy for the efficacy of its decisions.
Certainly one can disagree about the utility or efficacy of BDS as a tactic.
Yet it turns out that neither case provides any evidence for the efficacy of widespread surveillance programs.
The efficacy of bandying threats of going to hell met its match in the Civil War.
On average, the vaccine has an efficacy of about 60 percent.
To the efficacy and permanency of your union a government for the whole is indispensable.
Not every one in Germany is obsessed with a conviction of the efficacy of “frightfulness.”
He is a firm believer in the efficacy of brandy to keep out the cold.
So-and-so, with the efficacy of somebody sobbing or dancing in our presence.
He says that, "Like the immortal Washington, he believed in the efficacy of prayer."
1520s, from Latin efficacia "efficacy, efficiency," from efficax (genitive efficacis) "powerful, effective," from stem of efficere "work out, accomplish" (see effect). Earlier in same sense was efficace (c.1200), from Old French eficace (14c.), from Latin efficacia; also efficacite (early 15c.), from Latin efficacitatem.