Difference and nuance between することはない and する必要はない/する可能性はない


I understand the grammar point "Verb (Dictionary Form) + ことはない" can mean
either "There is no need" or "There is no possibility" depending on context.

However, what are the differences? Are there any nuances which I should be
aware of? Can they simply be interchanged in any circumstance?

"There is no need" example:

わざわざここに来る必要はない  
vs  
わざわざここに来ることはない

"There is no possibility" example:

今日の会議を忘れる可能性はない  
vs  
今日の会議を忘れることはない




When ことはない is used to mean “there is no need,” _I think_ that the nuance is
that it is not only unnecessary but also should be avoided. 必要はない on the
surface just states that it is unnecessary. (I wrote “on the surface” because
if someone _chooses_ to say that something is unnecessary, it is often because
he/she actually thinks that something should not be done. But the phrase 必要はない
itself does not mean “should avoid.”)

When ことはない is used to mean “there is no possibility,” I am not aware of any
difference in meaning from 可能性はない. 可能性はない sounds a little more explanatory and
argumentative than ことはない because of the use of the word 可能性 which is
semantically heavier than こと.




When ことはない is used to mean “there is no need,” _I think_ that the nuance is
that it is not only unnecessary but also should be avoided. 必要はない on the
surface just states that it is unnecessary. (I wrote “on the surface” because
if someone _chooses_ to say that something is unnecessary, it is often because
he/she actually thinks that something should not be done. But the phrase 必要はない
itself does not mean “should avoid.”)

When ことはない is used to mean “there is no possibility,” I am not aware of any
difference in meaning from 可能性はない. 可能性はない sounds a little more explanatory and
argumentative than ことはない because of the use of the word 可能性 which is
semantically heavier than こと.

