Efficacy

n.capable, hopefulprofessional

What it means

The demonstrated capacity of an intervention or method to produce its intended effect.

Reach for it when discussing whether something works under specified conditions

The controlled trial measured the treatment's efficacy against the agreed outcome.

playful
does it work?
when the technical question needs a plain-language heading
not when The question is accessible but too loose for a measured scientific property.
everyday
success rate
when a clear proportion of successful cases can be stated
not when A rate hides outcome size, study conditions, and what counts as success.
warm
impact
when the scale of change is more important than causal precision
not when Impact can be unintended or harmful and does not by itself show efficacy.
professional
effectiveness
when results in ordinary real-world use are being judged
not when Efficacy often concerns controlled conditions, so real-world effectiveness answers a different question.
professional
performance
when measured behavior across several criteria is relevant
not when Performance includes speed or reliability and need not establish the intended effect.
formal
potency
when the strength of an active agent matters
not when A potent agent can be powerful yet poorly targeted or unsafe.
formal
utility
when practical usefulness to a decision-maker is central
not when Utility includes convenience or preference, not merely causal ability.

clinical efficacy
Clinical efficacy was assessed before convenience or price.
demonstrated efficacy
Demonstrated efficacy justified a larger and more representative trial.
efficacy of treatment
The review separated the efficacy of treatment from its real-world availability.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.