[Vocabulary] Efficacy vs efficiency

[BallsOfSteel]

Hello,

The title speaks for itself and I don't seem to get the difference :-|. Some examples would be appreciated.

Thank you.

 

[SoothingDave]

"Efficacy" is not a commonly-used word. It means that something is able to produce the intended effect, to do what it is you want, to get the job done.

"Efficiency" is being able to do something with the least amount of effort or waste.

An Abrams tank, my Kia crossover SUV and a motorbike would all be efficacious in getting me from my home to work. But there would be varying degrees of efficiency involved in the three, in terms of cost and fuel use.

 

[Skrej]

But there would be varying degrees of efficiency involved in the three, in terms of cost and fuel use.

As well as parking.

 

[SoothingDave]

With the tank, I park wherever (and on top of whatever) I want.

 

[MikeNewYork]

"Efficacy" is very commonly used in medicine.

 

[tedmc]

Efficiency is often quantified in terms of percentage (input/output) whereas efficacy which is about achieving the desired effect is not.

 

[MikeNewYork]

"Efficacy" is often expressed in percentages. Antibiotic X has a 70% efficacy against Lyme disease.

 

[tedmc]

"Efficacy" is often expressed in percentages. Antibiotic X has a 70% efficacy against Lyme disease.

Does that mean the drug does not cure the disease completely?

 

[MikeNewYork]

No. It means that the drug does not cure 100% of the patients.

 

[Rover_KE]

Some examples would be appreciated.

Click here for more examples than you could possibly need, then change the search word to efficiency.

Bookmark the site for future reference.

 

[Barb_D]

As a simple summary:
Efficacy is how well something is done.
Efficiency is how few resources you need to use to get the desired results.

Let's say you have two teams of people who do data entry.
Team A has four people this week (one is on vacation) and Team B has five.
They have to process the same amount of work, and they do.
Team A is working with greater efficiency that week.
However, they make so many mistakes that 20% of their work has to be reprocessed. So Team B had greater efficacy.