Effeciency vs. effectiveness

[Mkostya]

Hi,
can you please explain the difference (with examples) of efficiency, effectiveness and efficacy?

Thanks

[Jamie (K)]

"Efficiency" means doing something with the least amount of time, energy or resources.

"Effectiveness" means doing something so that the task or the problem is resolved well.

"Efficacy" means performing well for the intended purpose. Usually medicines can be described as having "efficacy", or management techniques, for example.

[Mkostya]

Thank you very much !