"That is not a cat."

Translation: Das ist keine Katze.

[Zero937633]

Why not "Das ist nicht eine Katze"?

[az_p]

As a general rule, nicht + ein = kein.

[DWokeck]

Duolingo now accepts this answer.

[dritz47]

I did a translation earlier which was marked wrong: "Das ist keinen Apfel", Duolingo said it should be "Das ist kein Apfel" and in the comments section I understood the reasoning to be because Das is neutral and that takes precedence over Apfel which is male. I could be wrong and have asked for clarification on that forum listing.

But if the correct way of saying "that is not an apple" is "das ist kein Apfel" then why shouldn't "that is not a cat" be "das ist kein Katze"?

[mizinamo]

I did a translation earlier which was marked wrong: "Das ist keinen Apfel", Duolingo said it should be "Das ist kein Apfel" and in the comments section I understood the reasoning to be because Das is neutral and that takes precedence over Apfel which is male.

No; the reasoning is that you need the nominative case (e.g. der Apfel, kein Apfel) and not the accusative case (e.g. den Apfel, keinen Apfel) after sein "to be".

Here, Katze is feminine and so the nominative and accusative look the same; still, keine Katze is in the nominative here, not the accusative.

[adolf618982]

Why keine and not kein?

[mizinamo]

Why keine and not kein?

Because Katze is feminine, not masculine or neuter.

[targettaker]

Bcs katze is feminine and "kein" is used before neutral and masculine nouns.
So the katze is feminine and the only suitable word is "keine"

[alborghetti]

Why isnt 'dies' correct rather than 'das' at the start

[mizinamo]

Why isnt 'dies' correct rather than 'das' at the start

Because the English sentence has "that" and not "this".

dies is for things that are close to you = this, these

das is mostly for things that are far from you = that, those. It can also be used for close things = this, these.

[Xav_12]

i know its been said before, but would it still be correct if you said das ist nicht eine Katze

[TheSmokingGnu]

Okay, i am still trying to translate this things using nicht, this time it was:
Das ist der Katze nicht - no good.
How to negate a verb rather than object?

[mizinamo]

Das ist der Katze nicht - no good.

Right. Firstly, Katze is feminine; secondly, the English sentence has "a cat" and not "the cat".

So you would need not die Katze but eine Katze.

But since you're negating it, Das ist nicht eine Katze turns into Das ist keine Katze.

nicht as a separate word would be appropriate for a definite noun such as die Katze, but not for an indefinite noun such as eine Katze. (A bit simplified but a good rule of thumb.)

I suppose you could say that this is negating the object rather than the verb but that's the way it would be expressed in idiomatic German.

[sanjanasin299940]

What is different between keine,kein and keinen

[PeterCook575976]

Ok my answer was the same as response but still wrong why??

[mizinamo]

still wrong why?

Please show us your answer -- if you have a screenshot, upload it to a website somewhere (e.g. imgur) and tell us the URL.

Otherwise nobody can tell you what might have gone wrong.