Definition

The ability to produce a desired or intended result; effectiveness.

Example

The efficacy of the new drug was proven in clinical trials.

Conversation

Have you heard about the new study on the efficacity of that vitamin supplement?

Yeah, I read something about it; they say it's really effective.

I wonder if it actually lives up to its claims on efficacity.

Only one way to find out — we should try it ourselves!

Synonyms & Antonyms

Root Explanation

Efficacity → It is formed from "efficax" (from Latin, meaning effective or able to produce a desired effect) and the suffix "-ity" (meaning the state or quality of). The word "efficacity" refers to the quality of being effective or producing the intended result.

Memory Tip

Think of 'effective' when you hear 'efficacity' — it describes the quality of being able to produce the desired effect.

Visually Confused Words