"The cat does not have milk."
Translation:У кошки нет молока.
Why are we using кошки instead of кошка?? it's asking for "The cat does not have milk." Isn't кошки plural??
It's because it's in the prepositional case due to the У.
Edit: Corrected "genitive" to "prepositional" case
I've not understood: don't words finishing with -a change to -ы in genitive case?
Usually yes. But because of Russian spelling rules, after the letters г, к, х, ж, ч, ш, and щ, the -ы is written -и. The preposition у requires the genitive, not the prepositional. (If it were the prepositional case, it would be кошке)
Yes, you're right. I've edited my previous comment, so I think it's correct now.
OK but doesn't the preposition Y in the verb "to have" want genitive case? in any case I have just remembered that words finishing with -ka in the genitive case end with -kи
You're correct that кошки is plural...in the nominative case. But it is also the genitive singular form, and that's what's used here. The preposition у requires the genitive.
"Есть" is replaced by "Нет", meaning "There is no", instead of "Есть" which would mean "There is".
There's no such word as молокы in Russian. From what I've heard nominative молоко changes to genitive молока whenever you have нет, a negative.
I actually recommend wiktionary as a good source. It's very consice and provides the plural declensions as well as all conjugations for verbs.
I wrote "У кошки молока нет." and it was rejected. As far as I know, "У кошки его нет." is a correct sentence. I guess the position of the нет is determined by whether the object to be negated is a pronoun or not.