This page will make sure you never confuse efficacy and efficiency and proficiency again! Read the definitions, check out our example sentences, and be sure to follow the twitter feed to see how the internet is using these words in a sentence.
Got efficacy and efficiency and proficiency figured out? Check out the complete index of commonly confused English words.
Definition
1
Efficacy
Capacity or power to produce a desired effect
Examples
Concern about the safety and efficacy of the vaccine
2
Efficiency
The ratio of the output to the input of any system
Examples
She did the work with great efficiency
3
Proficiency
The quality of having great facility and competence
Examples
Practice greatly improves proficiency
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