Singular vs. Plural

Question

No leiste ningún libro de italiano.
For "any Italian books" why is this not "nigunos libros italianos"?

Answer

Hi Ricky,
Inside the lesson we are saying that the plurals (ningunos/ningunas) are not often used. Only with certain nouns that are used in their plural forms, e.g gafas (glasses), pantalones (trousers)...
Here are some examples: 
"No he comprado ningunas gafas de sol este verano.
-I didn't buy any sun glasses this summer.
" No tengo ningunos pantalones negros en mi armario.
I don't have any black trousers in my wardrove.

But, if it is a word that we use in singular and plural, e.g manzana/s, 
"No tengo ninguna manzana en mi frutero"
I don't have any apples in my fruit bowl.
I hope this makes it clearer for you.
Inma

Answer

Gracias otra vez, Inma.
I understand what you said but why it is done this way is still confusing.
Ricky

Answer

@Ricky.  I don't know if this will help at all, but ningunos/as is a pronoun .  Ningún/a is an adjective.  It's like the difference between saying "We don't have any books by Stephen King."  and "Are there any books by Stephen King left?"  " No, there aren't any."

Answer

In most cases that is.  There are a few rare exceptions when you use ningunos/as as an adjective, but Inma has already covered that.