Two questions decide the form
Every time you use кото́рый, ask two questions. The answers come from two different places, which is the one tricky part.
кото́рый in every case
кото́рый ends exactly like the adjective но́вый (new). The stress always stays on -то́-. In the accusative, the masculine and plural forms follow the animate rule: one form for things, another for people and animals.
| Case | Masculine | Feminine | Neuter | Plural |
|---|---|---|---|---|
| Nominativewho, which (subject) | ||||
| Genitiveof which, whose | ||||
| Dativeto which | ||||
| Accusativewhom, which (object) | ||||
| Instrumentalwith which | ||||
| Prepositionalin, about which |
One example in each case
English often drops “that” or “which” (“the book I’m reading”) and pushes the preposition to the end (“the house I live in”). Russian does neither: кото́рый is always there, and any preposition (a small linking word like в or с) comes straight before it.
“Whose”: кото́рого, кото́рой, кото́рых
To say “whose” inside a sentence, Russian uses the genitive of кото́рый, literally “of whom”. It goes after the thing owned, and agrees with the owner: кото́рого for a man, кото́рой for a woman, кото́рых for several people. This is a B2 structure, common in writing.
тот, кто… and всё, что…
After a pronoun rather than a noun (тот, “the one”; все, “everyone”; всё, “everything”; то, “that”), Russian uses кто for people and что for things instead of кото́рый. кто always takes a masculine singular verb, even after все.
где, куда́, отку́да, когда́
For places and times, the question words can do the job of кото́рый, exactly as English uses “where” and “when”. Both versions are correct: го́род, где я роди́лся = го́род, в кото́ром я роди́лся. Choose the place word by the same logic as in questions: где? (where at), куда́? (where to), отку́да? (where from).
Commas on both sides
Russian has no choice here: a relative clause is always fenced off by commas, at the start and, if the sentence continues, at the end. English only does this for extra, non-essential information. In speech the commas are heard as a slight pause.
The written alternative: participles
In books, news and formal writing, a кото́рый clause is often compressed into a participle: a verb form that behaves like an adjective, similar to English “reading” in “the student reading a book”. Recognising these is essential from B2; using them is a C1 skill. Full detail in participles.
Check yourself
Put кото́рый into the right form, or fill the gap with кто or что. Say the answer out loud, then reveal it.