Is effectivity a relevant word?

[Eden Darien]

I stumble upon a question from a friend about effectivity versus effectiveness as in "the effectiveness of a contract". I have checked thrice in dictionaries that both effectiveness and effectivity exist under entry "effective"

However some argue that 'effectivity' is not an English word, it is a common mistake that non-native speakers always do. Some say that they being native speakers haven't heard the word in their entire life hence assuming it as a mistake.

What say you?

 

[The Dude]

What I say is:

"Being a native English speaker, and not having heard the word 'effectivity' in my entire life, I assume it is a mistake."

Use 'effectiveness'. It's right.

 

[JMurray]

Eden.
It's true that "effectivity" sometimes occurs, usually in a very technical, written context, but I have never heard it spoken. For everyday use "effectivity" is so uncommon that it's probably best avoided for a learner. In the Corpus of American English there are 9374 citations for "effectiveness" and 5 for "effectivity" which indicates that "effectiveness" is going to cover pretty much any context you might need, especially when you consider that they are generally defined as having the same meaning.

PS: an example of a very technical context.
Effectivity

not a teacher

 

[Eden Darien]

Thank you very much!!

So I assume effectivity is a relevant word but has to be avoided...

 

[Tdol]

You find words creeping out of specialised use like that, but unless you really need to use it, it may come across as sloppy and inaccurate. This definition in UrbanDictionary shows the kind of reaction such jargon seepage can cause:

An idiotic modern word that has crept out of technical use in game theory to compete in pseudo-intellectual discourse with the real English word satisfying the same part of speech (effectiveness), which should be used instead in almost every case. Not to be confused with efficacy, which actually has a different meaning.
The effectivity of the word "effectivity" is nonexistent.

Urban Dictionary: effectivity