Here's a breakdown of noun declension in some languages:
German:
* Nominative: The subject of the sentence. (e.g., Der Mann ist groß. - The man is tall.)
* Accusative: The direct object of the sentence. (e.g., Ich sehe den Mann. - I see the man.)
* Dative: The indirect object of the sentence or recipient of an action. (e.g., Ich gebe dem Mann ein Buch. - I give the man a book.)
* Genitive: Shows possession or relationship. (e.g., Das Buch des Mannes - The book of the man.)
Latin:
* Nominative: Subject. (e.g., Puer est in horto. - The boy is in the garden.)
* Genitive: Possession. (e.g., Liber pueri - The boy's book.)
* Dative: Indirect object. (e.g., Pueri dono librum - I give a book to the boy.)
* Accusative: Direct object. (e.g., Video puerum - I see the boy.)
* Ablative: Used for various purposes, including means, time, place, and separation. (e.g., Venio a villa - I come from the house.)
Russian:
* Nominative: Subject. (e.g., Девушка читает книгу. - The girl is reading a book.)
* Genitive: Possession, partitive, or object of some prepositions. (e.g., Девушки нет дома. - The girl is not at home.)
* Dative: Indirect object. (e.g., Я даю книгу девушке. - I give a book to the girl.)
* Accusative: Direct object. (e.g., Я вижу девушку. - I see the girl.)
* Instrumental: Means or instrument. (e.g., Я пишу ручкой. - I write with a pen.)
* Prepositional: Used with certain prepositions. (e.g., Я думаю о девушке. - I think about the girl.)
English is an isolating language, meaning it has minimal inflection. We typically don't change noun forms to indicate grammatical function. Instead, we rely on word order and prepositions to clarify meaning.
Therefore, while "declining" nouns is a key concept in many languages, it's not something you need to worry about in English.