čí is the Czech word for "whose?" — the question word that asks about ownership. Where English keeps "whose" frozen in one shape no matter what it modifies ("whose dog," "whose dogs," "to whose dog"), Czech treats čí as an adjective: it agrees in gender, number, and case with the thing possessed, not with the unknown owner. Getting this agreement right is the whole challenge of the word, and it is precisely where English speakers stumble.
čí asks about an owner, and agrees with what's owned
When you ask Čí je to auto? ("Whose car is it?"), čí describes auto (neuter), so it takes the neuter form. Ask about a feminine thing and it shifts; ask in a different case and it shifts again.
Čí je to auto?
Whose car is that? (neuter)
Čí je tahle kniha?
Whose book is this? (feminine)
Čí je ten pes venku?
Whose is that dog outside? (masculine)
In the nominative singular, čí happens to look the same for all three genders (čí auto, čí kniha, čí pes) — which lulls learners into thinking it never changes. It changes plenty as soon as you leave the nominative.
How it declines: like a soft adjective
čí follows the soft adjective pattern — the same endings as jarní (see soft adjective declension). If you know that pattern, you already know čí.
| Case | Masculine | Feminine | Neuter | Plural (all genders) |
|---|---|---|---|---|
| Nominative | čí | čí | čí | čí |
| Genitive | čího | čí | čího | čích |
| Dative | čímu | čí | čímu | čím |
| Accusative | čího (anim.) / čí (inanim.) | čí | čí | čí |
| Locative | čím | čí | čím | čích |
| Instrumental | čím | čí | čím | čími |
Notice that the feminine singular is čí in every single case — feminine never changes, which is a small mercy. The masculine and neuter, on the other hand, run through čího, čímu, čím just like jarního, jarnímu, jarním.
čí across genders and cases — examples
The masculine animate accusative (asking about an owned person or animal) is the form learners most often get wrong, because it must take -ho:
Čího psa to tady venčíš?
Whose dog are you walking out here? (masc. anim. accusative)
Čího bratra jsi včera potkal?
Whose brother did you meet yesterday?
The genitive (often "whose ... is it part of?"):
Z čího účtu se to platilo?
Whose account was it paid from? (masc. genitive after z)
The dative:
Čímu dítěti patří ta bunda?
Whose child does that jacket belong to? (neuter dative)
The instrumental, frequently in the set phrase asking for help or means:
S čí pomocí jsi to dokázal?
With whose help did you manage it? (feminine instrumental — pomoc is feminine, so čí stays čí)
Čím autem pojedeme?
Whose car will we take? (neuter instrumental)
And the plural:
Čí jsou tyhle boty u dveří?
Whose shoes are these by the door? (plural)
čí versus kdo and the genitive koho
It is worth keeping three "who"-type questions apart. kdo asks who (the person, as subject or object). Its genitive koho asks "of whom / whose" in the sense of identifying a person. čí asks specifically about ownership and agrees adjectivally.
| Word | Asks | Behaves like | Example |
|---|---|---|---|
| kdo | who? (person) | a noun-pronoun | Kdo to udělal? |
| koho (gen. of kdo) | of whom / whose (as a person) | genitive of kdo | Koho je to syn? |
| čí | whose? (possessor) | a soft adjective | Čí je to syn? |
Čí je to dům?
Whose house is it? (standard, adjectival — the everyday choice)
Koho je to dům?
Whose house is it? (colloquial — using the genitive of 'who')
Both questions get answered the same way, but čí is the neutral, standard option and the one to default to. The koho version (the genitive of kdo doing the job of "whose") is heard in casual speech but feels lower-register; treat it as something to recognise rather than your go-to. See kdo & co for the full declension of kdo.
The relative use: ten, čí…
Beyond questions, čí can introduce a relative clause meaning "whose" — "the man whose car was stolen." In modern Czech this relative čí is fairly bookish; everyday speech far more often reshapes the sentence with jehož / jejíž / jejichž (the relative possessives) or with kterému patří. Still, you will meet relative čí, especially correlated with a demonstrative:
Vyhraje ten, čí návrh bude nejlepší.
The one whose proposal is the best will win.
Pomůžeme tomu, čí situace je nejtěžší.
We'll help the one whose situation is the hardest. (dative tomu, čí situace)
For the broader correlative pattern (ten… který…, ten… čí…), see ten… který correlatives.
How English differs
This is the crux. English whose is invariable — one word for every gender, number, and case. Czech čí is an adjective that must agree with the possessed noun. So an English speaker, hearing "whose dog do you see," is tempted to keep čí flat and say čí pes vidíš — but because pes is the object, both the noun and čí go accusative: Čího psa vidíš? The mental move you must make is: first decide what case the owned thing is in, then put čí in that same case. English never asks you to do this, which is exactly why it feels alien at first.
Common Mistakes
❌ Čí psa vidíš na zahradě?
Incorrect — the dog is a masculine animate object, so čí must be accusative čího.
✅ Čího psa vidíš na zahradě?
Whose dog do you see in the garden?
❌ S čího pomocí jsi to udělal?
Incorrect — pomoc is feminine, so čí stays čí, and the masc. form čího is wrong.
✅ S čí pomocí jsi to udělal?
With whose help did you do it?
❌ Čí auto pojedeme?
Incorrect — 'by whose car' needs the instrumental: čím autem.
✅ Čím autem pojedeme?
Whose car will we go in?
❌ Koho je to kniha?
Understandable but low-register and dispreferred for asking ownership.
✅ Čí je to kniha?
Whose book is it? (standard)
❌ Čímu dítě patří ta hračka?
Incorrect — the child is dative here, so both words must be dative: čímu dítěti.
✅ Čímu dítěti patří ta hračka?
Whose child does that toy belong to?
Key Takeaways
- čí = "whose?" and declines like the soft adjective jarní: čí / čího / čímu / čí / čím / čím.
- It agrees with the possessed noun in gender, number, and case — never with the (unknown) owner.
- Feminine singular is čí in all cases; masculine and neuter run čího, čímu, čím.
- The biggest trap: forgetting to decline it. "Whose dog do you see?" = Čího psa vidíš?, not Čí pes vidíš.
- koho (genitive of kdo) can mean "whose" colloquially, but čí is the standard, neutral choice.
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- kdo and co: Who and WhatA2 — The pronouns kdo (who) and co (what) as both question words and relatives, with their full declension and their fixed singular agreement.
- který: The Main Relative PronounB1 — který/která/které declined as a hard adjective, the workhorse relative 'which/that/who'.
- Possessive Pronoun vs Genitive of the PronounB2 — When to say jeho dům vs constructions with the genitive, and the jeho ambiguity.
- Soft Adjectives: the -í PatternA2 — The soft adjective class — model jarní — uses a single -í ending for masculine, feminine, and neuter alike, giving it far fewer distinct forms than the hard type.
- The Correlative ten ... kterýB1 — Building relative clauses with a ten antecedent and a který relative pronoun.