The word ‘impact’ is countable as well as uncountable.

Some are countable as well as uncountable depending on their use. One of the example of this kind of nouns is ‘impact’.

1) When ‘impact’ means “the effect or influence that an event, situation etc. has on someone or something”, it is countable.Example:The impact of peer pressure on teenagers tends to be reflected in certain types of behavior.

2) When ‘impact’ means “the force or one object hitting another”, it can be countable or uncountable depending on how it is used. – When ‘impact’ is used to mean a number of different forces, it is countable.Example : The impacts of momenta are not easy to control. -When ‘impact’ means the collective force or one object hitting another it is uncountable.Example: The impact of the vehicles hitting the wall was sufficient to damage the building.

There are few more words such as ‘technology’ and ‘development’ which can be used as countable as well as uncountable. But I won’t go in their details. Hope this helps 🙂