The Pronoun "Чей" (Whose)
When you want to ask who owns something or establish the origin of an item, you use the interrogative pronoun чей (whose). Like an adjective, чей must agree with the noun it modifies in gender, number, and case.
Here is the full declension table for чей:
| Case | Masculine & Neuter | Feminine | Plural |
|---|
| Nominative | чей / чьё | чья | чьи |
| Accusative | чей (чьего) / чьё | чью | чьи (чьих) |
| Genitive | чьего | чьей | чьих |
| Dative | чьему | чьей | чьим |
| Instrumental | чьим | чьей | чьими |
| Prepositional | чьём | чьей | чьих |
(Note: In the Accusative case, masculine and plural forms take the Genitive form if the noun is animate, and the Nominative form if inanimate.)
Genitive Case
You will often need the Genitive form чьего (masculine/neuter), чьей (feminine), or чьих (plural) to show possession ("of whose..."), or after prepositions that require the Genitive, such as около (near).
Dative Case
Use the Dative forms чьему, чьей, or чьим when indicating direction with the preposition к (towards), or with verbs like принадлежать (to belong to), which require the owner to be in the Dative case.
Instrumental Case
The Instrumental forms чьим, чьей, and чьими are used with the preposition с (with) or after verbs that govern the Instrumental case, such as интересоваться (to be interested in).
Prepositional Case
When talking about locations using в (in) or на (at/on), use the Prepositional forms чьём, чьей, or чьих.
Accusative Case and Plurals
When "whose" modifies the direct object of a sentence, use the Accusative case. For feminine nouns, this is always чью.
When referring to the origin or details of multiple items, use the plural oblique forms, such as the plural Genitive чьих.