It depends on how the word paper is used. If you are referring to the type or class of substance that is paper, it is an uncountable noun. If you are referring some forms of paper, it is a countable noun. Examples:
Uncountable: Do you prefer paper or plastic. China is now the leading paper producing country. Use two pieces of paper to wrap each purchase.
Countable: These papers are published monthly. I had to submit two science papers this week.
The noun stationery is an uncountable noun, an aggregate noun, a word for a combination of things included in one word. The noun stationery can be simply writing paper, or any type of office materials.
The noun 'stationery' is an uncountablenoun, a form of aggregate noun, a word representing an indefinite number of elements or parts.
Transport is both countable and uncountable as a noun.
countable
uncountable
Uncountable
The gerund painting is a countable noun, as in "There are 12 paintings in this room."
Transport is both countable and uncountable as a noun.
countable
Uncountable
uncountable
Uncountable
uncountable
uncountable
The gerund painting is a countable noun, as in "There are 12 paintings in this room."
Countable
countable
few is countable
The noun 'steel' is an uncountable (mass) noun, a word for a substance.