Кто and что as case systems
Кто and что have case forms. They do not behave like regular nouns, but the forms are predictable enough to learn through sentence frames.
Кто:
- кто — who, nominative
- кого — whom / whose, accusative or genitive
- кому — to whom, dative
- кем — by/with whom, instrumental
- о ком — about whom, prepositional phrase
Examples:
- Кто написал письмо? — Who wrote the letter?
- Кого ты ждёшь? — Whom are you waiting for?
- Кому он звонил? — Whom did he call?
- Кем она работает? — What does she work as? Literally, as whom.
- О ком идёт речь? — Who is being discussed?
Что:
- что — what, nominative or accusative
- чего — of what / what, genitive
- чему — to what, dative
- чем — by/with what, instrumental
- о чём — about what, prepositional phrase
Examples:
- Что произошло? — What happened?
- Что ты читаешь? — What are you reading?
- Чего не хватает? — What is missing?
- Чему нас учит этот пример? — What does this example teach us?
- Чем ты пишешь? — What are you writing with?
- О чём ты думаешь? — What are you thinking about?
A serious learner should hear case inside the question. Кому? already tells you that the unknown person is a dative participant. Чем? tells you the unknown item may be an instrument, means, or predicate complement.
Какой: quality, type, and description
Какой agrees with the noun it asks about:
- какой вопрос? — what kind of question? masculine
- какая книга? — what kind of book? feminine
- какое правило? — what kind of rule? neuter
- какие ошибки? — what kind of errors? plural
It can ask about quality:
- Какой фильм? — What kind of film? / What is the film like?
- Какая у него работа? — What kind of job does he have?
- Какое это слово: книжное или разговорное? — What kind of word is this: bookish or conversational?
It can also ask for identification by type where English uses “what.”
- Какой у вас вопрос? — What is your question? Literally, what kind of question do you have?
- Какая сегодня дата? — What is today’s date?
- Какой это падеж? — What case is this?
Learners often overuse что here. Что падеж? is not standard Russian for “What case?” The expected question is Какой это падеж? or В каком падеже стоит слово?
Который: which from a set, sequence, and time
Который asks “which one” when the set is already present or implied. It also asks about order or number in a sequence.
- Которую книгу ты выбрал: первую или вторую? — Which book did you choose: the first or the second?
- Который из этих вариантов правильный? — Which of these options is correct?
- Которая дверь ведёт в аудиторию? — Which door leads to the classroom?
- Который час? — What time is it?
- На котором этаже вы живёте? — Which floor do you live on?
Какой and который can overlap, but the emphasis differs.
- Какую книгу ты ищешь? — What kind of book / which book are you looking for? Open-ended.
- Которую книгу ты ищешь? — Which book, among known options, are you looking for?
In many real situations, native speakers may choose either depending on context, but learners should still understand the difference: какой asks about quality/type or open selection; который points to a defined set or sequence.
Чей: whose, with agreement
Чей asks about possession and agrees with the possessed noun:
- чей дом? — whose house?
- чья книга? — whose book?
- чьё письмо? — whose letter?
- чьи документы? — whose documents?
Case forms matter:
- Чьего брата ты видел? — Whose brother did you see?
- Чьей сестре ты звонил? — Whose sister did you call?
- С чьими друзьями ты говорил? — With whose friends did you speak?
- О чьей работе идёт речь? — Whose work is being discussed?
Again, the form agrees with the possessed noun, not the owner. Чья машина? because машина is feminine. Чей отец? because отец is masculine.
Questions with prepositions
Russian often keeps the preposition before the interrogative pronoun:
- О чём ты думаешь? — What are you thinking about?
- С кем ты говорил? — Who did you speak with?
- К кому она пошла? — To whom did she go?
- У кого есть словарь? — Who has a dictionary?
- Для чего это нужно? — What is this needed for?
- Из-за чего возникла проблема? — Because of what did the problem arise?
English may move the preposition to the end in informal speech. Russian does not imitate that pattern. The preposition is a strong case signal.
Contrast sets
Кто vs что
- Кто пришёл? — Who came?
- Что произошло? — What happened?
Что vs какой
- Что ты читаешь? — What are you reading?
- Какую книгу ты читаешь? — What kind of book / which book are you reading?
- Что это? — What is this?
- Какое это слово? — What kind of word is this?
Какой vs который
- Какой фильм ты хочешь посмотреть? — What kind of/which film do you want to watch? Open.
- Который фильм ты хочешь посмотреть: первый или второй? — Which film do you want to watch: the first or the second?
Чей agreement
- Чей это дом? — Whose house is this?
- Чья это книга? — Whose book is this?
- Чьё это письмо? — Whose letter is this?
- Чьи это ключи? — Whose keys are these?
Common learner misreadings
The first error is using что for all English “what” questions. Russian often wants какой when asking about type, quality, or category.
The second error is ignoring case in кто / что forms. Кого ты помог? is wrong because помогать takes dative: Кому ты помог?
The third error is using который as a general “which” without a set. It is strongest when choices are known or ordered.
The fourth error is making чей invariable. Чей книга? should be чья книга?
The fifth error is separating prepositions from question words in English order. Russian asks с кем, о чём, для кого, not “кто с” or “что о.”
Build a question-word decision tree. Ask:
- Is the unknown a person? Use кто and choose case.
- Is the unknown a thing/event/content? Use что and choose case.
- Are you asking about type or quality? Use какой.
- Are you choosing from a known set or sequence? Use который.
- Are you asking about owner? Use чей and make it agree.
Then convert statements into questions:
- Она помогла брату. → Кому она помогла?
- Мы говорили о падежах. → О чём мы говорили?
- Это сложный текст. → Какой это текст?
- Он выбрал вторую книгу. → Которую книгу он выбрал?
Interrogative pronouns are often taught as vocabulary items, but serious Russian study must treat them as grammatical instruments. Each question word asks for a category of information and also takes the case required by its role in the sentence.
Begin with кто and что. They are not interchangeable with English “who” and “what” in every syntactic environment; they decline:
- Кто пришёл? — Who came?
- Кого ты видел? — Whom did you see?
- Кому ты звонил? — Whom did you call? / To whom did you phone?
- С кем ты говорил? — With whom did you speak?
- О ком ты думаешь? — About whom are you thinking?
For что:
- Что случилось? — What happened?
- Что ты читаешь? — What are you reading?
- Чего ты боишься? — What are you afraid of?
- К чему это приведёт? — What will this lead to?
- О чём статья? — What is the article about?
The key habit is simple: do not choose the case by the English question word. Choose it by the Russian verb, preposition, and sentence role.
Now separate какой, который, and чей:
- Какой словарь тебе нужен? — What kind of dictionary do you need?
- Который словарь ты выбрал? — Which dictionary did you choose, from a known set? This is more restricted and less common than learners expect.
- Чей это словарь? — Whose dictionary is this?
Какой asks for type, quality, description, or selection in broad terms. Который often asks “which one in an ordered or known set” and is also the main relative pronoun. Чей asks possession and agrees with the possessed noun:
- чей дом, чья книга, чьё письмо, чьи документы
- чью книгу ты нашёл? — Whose book did you find?
- о чьём докладе идёт речь? — Whose report is being discussed?
Include что за because real Russian uses it constantly:
- Что это за слово? — What kind of word is this?
- Что за странный пример? — What a strange example / what kind of strange example?
It can be neutral, curious, skeptical, or evaluative depending on intonation and context.
One of the best drills is to build the answer first and then turn it into a question. If the answer is с преподавателем, the question must be с кем? If the answer is о падежах, the question must be о чём? If the answer is старый академический словарь, the question may be какой словарь? This reverse-question method prevents English-driven errors.
Try it with five short answers and preserve the preposition and case every time: у Анны, к Ивану, с новым преподавателем, о русской грамматике, из старого архива.
Final rule
Russian interrogatives are not interchangeable translations of English question words. Choose кто/что for identity and content, какой for type, который for selection from a set, and чей for ownership — then put the question word into the case required by the sentence.