1 Use of the plural suffix
How would you tranlate 'several books' into Turkish? 'Birkaç kitap', or 'Birkaç kitaplar'?
We do not add the plural suffix to nouns after these words: birkaç (some, a few, several), çok (a lot of, many), az ([a] few) and hiç (any).
Look at these examples:
In the same way we do not pluralize nouns preceded by numbers:
2 Compound nouns
Why is the other one is incorrect?
We form these compounds simply putting two nouns together. We ALWAYS add the suffix -i (-ı, -ü, -u) to the second noun.
As in the last example, if the second noun ends in a vowel, the buffer letter s goes in between.
If, however, the second noun is su (water), the buffer letter y is used instead of s.