это твоя сестра vs. Эта кошка наша?
In comparing это твоя сестра with эта кошка наша, I was wondering why the 'эта' in the second sentence agrees in gender with 'кошка,' whereas the 'это' in the first sentence is masculine whereas the rest of the sentence is in the feminine. Can anyone help me figure this out? Thanks in advance!
For the same reason you can say "It is our cat" but not "It cat is ours". In Russian, это can mean a modifier "this" (which is attached to a noun) or just "this object" that forms a separate entity in the sentence. Adjectival modifiers agree with the noun they modify. "This is"-sentences start with "Это" regardless of the gender and number of what follows.
Having an English background can make it confusing because you do keep the agreement of "this/that" in such sentences, at least when it comes to singular/plural. Russian does not:
- Это моя кошка. = This is my cat.
- Это мои кошки. = These are my cats.
Now, let's move "это" to the position of a modifier, and move "моя" to the predicate:
- Эта кошка моя. = This cat is mine
- Эти кошки мои. = These cats are mine.
Theron126 has already linked you to a sticky post by olimo—perfect in case you find the use of these two words confusing.
"Это" has two functions. It's the neuter form of "This", and it can mean "This is". All of the other "Этот" forms don't share this function.
The difference between your two sentences is that the first one translates as "This is", and not "This + [noun]".
I guess 'ета' can also mean 'this is' too, though? I was confused as to why in the second sentence it's 'ета кошка..." instead of "ето кошка"
No. "Эта кошка" always means "This cat". Same with all the other "Этот" forms. In your sentence, the "Is" comes between "This cat" and "Yours", instead of "This" and "Your cat".
You could say "Это наша кошка", meaning "This is/Is this your cat".
That makes sense. So is the sentence "эта кошка наша" grammatically incorrect?
No, that's correct grammar. The difference between "Эта кошка" and "Это кошка" is the same as "This cat" and "This is a cat".
I don't have too much formal Russian education, but my guess is that the confusing part is the missing to be verb (as you know, Russian doesn't use to be in the present tense). It might help if you look at the sentences like this:
"Это - твоя сестра" (This is your sister) "Эта кошка - наша" (This cat is ours)
Where the "-" are the 'missing' to be verbs.
In the first one, you're saying "This -is- your sister," and 'this' doesn't have to agree with the object because it is the subject. But in "This cat -is- ours," "This cat" is the subject, so "this" has to agree in gender and case with "cat."
Hope I was able to help.