Uncountable: When referring to paper as a general substance or material, it is uncountable.
* Examples:
* "I need more paper to write on."
* "This sculpture is made of paper."
* "There's a lot of paper in the recycling bin."
Countable: When referring to paper as individual sheets or documents, it is countable.
* Examples:
* "Can you hand me three papers?" (referring to sheets of paper)
* "He has written several papers on this topic." (referring to research papers)
* "There are five papers in this pile." (referring to individual documents)
In summary:
* Uncountable: Paper as a general substance.
* Countable: Paper as individual sheets or documents.