Borrowing from Arabic قِرْطَاس (qirṭās).
karatasi (n class, plural karatasi)
1) paper (material for writing on)
How high is the percentage of finding a foreign language not related to yours having so many cognates from the same source? I tell you, Not. That. Much! Oh, and also, is paper the word's only meaning or does it have another associated with it?
Swahili has a lot of loan words from Arabic. Although it is not a Semitic language, but a Bantu language, a totally different language family, not even related to the Semitic languages as far as linguistical studies have shown, it has had a very extensive area of contact during the 1500 and onward with Arabic. It was used as a trade language, and has borrowed many words from the different peoples that the Bantus of the coastal region of Africa would trade with. Many locals would say that it is a mixed language, but the grammar is distinctly Bantu, although quite simplified compared to other Bantu languages. The influence is seen mainly through borrowed words. A bit similar to all the borrowings of Latin and French words that you find in English.
Yes, it could. Nouns in the N- class don't in general have a plural. I think there are some exceptions. If you want to specify whether you need just one or several pieces of paper you do that by changing the verb. Besides conjugating for the subject, the verb can also take an object concord marker. For this case you could write "Ninaihitaji karatasi" for the singular and "Ninazihitaji karatasi" for the plural.
Besides, if you want to specify that you need exactly one piece of paper, instead of just some unspecified amount of paper, I would probably say "Ninahitaji karatasi moja", for "I need one paper", instead of just "Ninahitaji karatasi".
Well yes, it's obvious the subject is singular. I was talking about the paper: "a paper" versus "paper" or "papers"
But, back to the question. I think you can translate karatasi as both 'paper' and 'papers'.
Karatasi is in the n-class.
So, yeah. You can use 'I need papers'.