When using a number in front of a noun, the noun is always in its singular form, so it does not receive the plural suffix -lEr.

Two cats are playing in the garden.

Bahçede iki kedi oynuyor.

Turkish speakers often use the word tane between a number and a noun, meaning something like pieces of. The word tane is also used when the noun is left out altogether.

Six eggs please.	Altı tane yumurta lütfen.
I want five.	Beş tane istiyorum.

Besides numbers, several quantifiers can be used to indicate amounts. In general, nouns are also in their singular form after these quantifiers.

There is an exception however. When a noun follows the quantifier bazı it is normally followed by the plural suffix.

Two cats are playing in the garden.	Bahçede iki kedi oynuyor.
Some dogs are very small.	Bazı köpekler çok küçük.
There are several cats.	Birkaç kedi var.
There are a lot of cats in the garden.	Bahçede birçok kedi var.
There is no cat.	Kedi yok.
There is not any cat at all.	Hiç kedi yok.
There is not a single cat.	Hiçbir kedi yok.

Breakdown of Onun dört kedisi bahçede.