The word stationery is uncountable. It refers to writing materials such as paper, envelopes, pens, and other office supplies as a collective category, without focusing on individual items.
Example sentences:
- Correct: “I need to buy some stationery for my office.”
- Incorrect: “I need to buy stationeries.”
If you want to refer to specific items, you would use countable nouns like pens, notebooks, or envelopes instead.