Question

На какие вопросы отвечают существительные,изменяясь по падежам?

Answer 1

Именительный падеж кто? что?
Родительный падеж кого?чего?
дательный падеж кому? чему?
винительный падеж кого?что?
творительный падеж кем?чем?
предложный падеж о ком? о чем?

Answer 2

What questions do nouns answer by changing forms (declension)?

Nouns change forms to indicate case. The case of a noun shows its grammatical function in a sentence. In Russian, there are six cases that nouns can take:

- Nominative case indicates the subject of the sentence. Example: "Мальчик играет." (The boy is playing.)

- Genitive case indicates possession or attributes. Example: "Книга мальчика." (The boy's book.)

- Dative case indicates indirect object. Example: "Я дал книгу мальчику." (I gave the book to the boy.)

- Accusative case indicates direct object. Example: "Я вижу мальчика." (I see the boy.)

- Instrumental case indicates means or accompaniment. Example: "Я играю с мальчиком." (I'm playing with the boy.)

- Prepositional case indicates location. Example: "Я иду к мальчику." (I'm going to the boy.)

So in summary, nouns change forms through declension to indicate grammatical functions like subject, object, possession, and other roles in a sentence. The six cases of Russian grammar are what determine the form a noun takes.