What is Efficacy?

The definition of efficacy is to perform a task to a satisfactory degree. It’s the ability to accomplish something and produce a desired result.
In the technical sense, it also refers to how well a drug, treatment, or product works.

Key Takeaways

  • efficacy is the power to produce a desired effect or result
  • it is also how well a product/drug works
  • common synonyms are effectiveness and efficiency

Understanding Efficacy

Efficacy is the perfect word to describe if something (or someone) produces a result you want. When discussing a product’s efficacy, you’re talking about its effectiveness and ability to do what it is supposed to.
The word itself comes from the Latin efficãcia, from 1520-30, and it was considered the equivalent of efficãc (effective).

Because of its positive/beneficial meaning, it can be a great way to illustrate how efficient a product is, for example: “that moisturizer has an 80% efficacy in fighting my seasonal dry skin!”


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