1. The degree to which something is successful in producing a desired result; success.
e.g. "The treatment has demonstrated its effectiveness at curing patients"

How often is it used?

The noun effectiveness appears just under half a million times in our database of scientific texts. It occurs more frequently in academic writing than in all other discourse genres of the Corpus of Contemporary American English combined (such as fiction writing, newspaper and magazine writing, blogs, and websites).

In our analysis of 250,000 abstracts taken from our database, the word effectiveness was shown to occur in three of 36 most frequent phrases we extracted. It is especially used towards the end of abstracts, when stating the meaning of results and the contribution of the research (e.g. X demonstrates the effectiveness of …).

Which words go with it?

Below is a list of some verbs, nouns, and adjectives frequently co-occurring with effectiveness in Writefull’s scientific database of published papers. These are called collocates.

Note that effectiveness should almost always be used with the definite article.

How to choose between effectiveness, efficacy, or efficiency

So how do you decide between the word effectiveness and other similar-sounding words such as efficacy or efficiency in your sentence? This is tricky, but two strategies can help.

First, you can use Writefull’s ‘Compare Words In Context’ search to see which one is more commonly used in a given phrase. The search results below show that while the verb measure is much more often followed by effectiveness than efficacy, compare is about as likely to be followed by one as the other.

Second, it is always helpful to consider possible nuances in meaning. These might be found by examining each sentence in context, or by checking a dictionary.

While efficacy and effectiveness may be used interchangeably, each may also have a very specific meaning in certain disciplines. In Medicine, efficacy is the degree of success of a treatment or method under ideal and controlled circumstances, while effectiveness is how well it performs in the real world.

On the other hand, efficiency can be defined as the ability to achieve something with the least amount of time, money, or effort.

*Definition from Oxford Languages

About the author

Mélodie is an Applied Linguist at Writefull.