In English, the words _efficacy_ and _effectiveness_ are often used interchangeably. If something is described as _efficacious_ or _effective_, it means it achieves the desired outcome. ^2213e4 However, in the medical field, _efficacy_ and _effectiveness_ are not synonymous. An intervention is considered _efficacious_ if it produces the desired result under ideal or controlled conditions, like in a lab setting. The same intervention is labeled _effective_ when it achieves the desired result in real-world, routine clinical conditions. ^07fc27 Interestingly, many other languages don’t distinguish between these terms and use the same word for both efficacy and effectiveness. Confusing these terms can lead to significant consequences, including misleading expectations, flawed downstream decisions, and unintended outcomes. While _efficacy_ and _effectiveness_ focus on the result, _efficiency_ is all about the process. A process is deemed _efficient_ when it achieves the desired outcome with the least amount of resources or effort. ^a9182b