These three terms are commonly used in everyday communication, but they’re often misunderstood or misused. After some research, here’s my own conceptualization of these terms, along with simple examples to help clarify them.

Efficacy

Efficacy is about accomplishing the goal—simply getting things done.

  1. When you fire a gun and hit the target, you are efficacious.
  2. When the solution you propose at work successfully solves a problem, you are efficacious.
  3. When you set out to write a book and complete it, you are efficacious.
  4. When you develop a medication that cures diabetes, it demonstrates efficacy.

Effectiveness

Effectiveness is about doing the right things to achieve the goal in a valuable and meaningful way.

  1. When you fire a gun and hit the target precisely in the center, you are effective.
  2. When the solution you propose at work not only solves the problem but does so in a long-term, sustainable way without needing further adjustment, you are effective.
  3. When your completed book is grammatically correct, well-structured, easy to read, and engaging for the reader, you are effective.
  4. When you develop a diabetes medication that cures the disease and also reduces the need for ongoing monitoring, you demonstrate effectiveness.

Efficiency

Efficiency is about achieving the goal while using the least amount of resources possible.

  1. When you fire a single, well-aimed shot with minimal gunpowder to hit the target accurately, you are efficient.
  2. When the solution you propose at work solves the problem flawlessly with minimal resources—such as a small team and only one technology—without disrupting other processes, you are efficient.
  3. When you write a book that is clear, engaging, and completed quickly, you are efficient.
  4. When you develop a diabetes medication that requires only a single pill and eliminates the need for ongoing patient monitoring, you are very efficient.

Summary

  • Efficacy means getting things done. (Is it working?)
  • Effectiveness means doing the right things. (Is it working well?)
  • Efficiency means doing things right. (Is it working in the most economical way?)

Efficiency can be seen as the final step in the loop, coming after efficacy and effectiveness. It’s about optimizing daily work, refining established processes, and gradually reducing resource use without compromising efficacy or effectiveness.