A relative pronoun stitches a second clause onto a noun: the man *who lives here, the book **that I'm reading, the house **in which I live. English mostly gets by with *who, which, and that, and often drops the pronoun entirely (the book I'm reading). Polish does none of that. Its workhorse relative pronoun który is a full adjective-like word that declines for gender, number, and case, can never be omitted, and is always preceded by a comma. Getting który right is the gateway to writing real Polish sentences instead of strings of short ones.
The core skill: agreement up, case from inside
Here is the rule that, once internalised, unlocks every relative clause in the language:
który takes its gender and number from the noun it refers to (its antecedent), but it takes its CASE from the role it plays inside the relative clause.
These are two independent decisions. Walk through them every time:
- Look back at the noun being described. Is it masculine, feminine, or neuter? Singular or plural? That fixes the stem of który — który (m.), która (f.), które (n./non-masculine plural), którzy (masculine-personal plural).
- Look forward into the relative clause. What job does the pronoun do there — subject, direct object, object of a preposition? That fixes the case ending.
Watch all three of the opening examples resolve:
| Phrase | Antecedent | Role in clause | Form |
|---|---|---|---|
| mężczyzna, który tu mieszka | mężczyzna (m. sg.) | subject | nominative który |
| książka, którą czytam | książka (f. sg.) | direct object of czytam | accusative którą |
| dom, w którym mieszkam | dom (m. sg.) | object of w | locative którym |
To jest mężczyzna, który mieszka obok mnie.
That's the man who lives next to me.
Książka, którą czytam, jest naprawdę wciągająca.
The book I'm reading is really gripping.
Dom, w którym dorastałam, już nie istnieje.
The house I grew up in no longer exists.
The gender stays glued to the antecedent (feminine książka → feminine którą no matter what), while the case floats according to the verb or preposition inside the clause. This is exactly the dual logic of kto/co in questions, now stretched across two clauses.
który across the cases
Because który takes whatever case its job demands, you will meet it in all six. A few worked examples by case, all referring to people or things of different genders:
Nominative — który is the subject of its clause:
Mam kolegę, który świetnie gotuje.
I have a friend who cooks brilliantly.
Genitive — here triggered by bać się (to fear), which governs the genitive:
To jest pies, którego wszyscy się boją.
That's the dog everyone is afraid of.
Dative — który is the indirect object of pomóc (to help):
Studentka, której pomogłem, zdała egzamin.
The student (f.) I helped passed the exam.
Accusative — direct object, with the masculine animate form looking like the genitive:
Lekarz, którego polecasz, jest na urlopie.
The doctor you recommend is on holiday.
Instrumental — object of z (with):
To ta koleżanka, z którą pracowałam w Krakowie.
That's the colleague (f.) I worked with in Kraków.
Locative — object of o (about):
Film, o którym wszyscy mówią, w końcu obejrzałem.
I finally watched the film everyone's talking about.
Notice that the preposition always travels with który to the front of the relative clause — z którą, o którym, w którym — never stranded at the end. The English habit of saying "the colleague I worked with" must become "the colleague with whom I worked" in Polish word order: koleżanka, z którą pracowałam.
The comma is obligatory
In English the comma before a relative clause is meaningful — it distinguishes a non-restrictive clause (my brother, who lives in Gdańsk, is a doctor) from a restrictive one (the man who lives here). In Polish there is no such choice: a relative clause introduced by który (or any subordinator) is always set off by a comma, restrictive or not. The comma marks the clause boundary, full stop.
Samochód, który kupiłem w zeszłym roku, ciągle się psuje.
The car I bought last year keeps breaking down.
Wszyscy, którzy przyszli, dostali prezent.
Everyone who came got a present.
When the relative clause sits in the middle of the main clause, it is fenced off with a comma on both sides, as in the samochód example above. Forgetting the comma is the most common punctuation error English speakers make in Polish.
którzy vs. które in the plural
The plural splits the way every Polish plural does, by the masculine-personal distinction. Use którzy when the antecedent is a group that includes at least one male person; use które for everything else — groups of women, animals, and things.
To są studenci, którzy zdali egzamin.
These are the students (incl. men) who passed the exam.
To są książki, które właśnie wyszły.
These are the books that have just come out.
Znam kobiety, które tam pracują.
I know the women who work there.
jaki — the qualitative relative
While który identifies which specific one, jaki picks out a kind or quality, and it pairs naturally with the demonstrative taki ("such") in the main clause: taki…, jaki… = "the sort that…". Compare:
Szukam mieszkania, które widziałem w internecie.
I'm looking for the (specific) flat I saw online — który, a particular one.
Szukam takiego mieszkania, jakie widziałem w internecie.
I'm looking for the kind of flat (like the one) I saw online — jaki, a type.
In everyday speech the line blurs and który often covers both jobs, but jaki is the precise choice when you mean "of the sort that". See /grammar/polish/determiners/which-what/ktory-jaki-czyj for the determiner uses side by side.
Relative co
Polish also has a relative co, used in two main situations. First, colloquially (informal/regional) as a stand-in for który — very common in speech, frowned on in careful writing:
Ten facet, co tu wczoraj był, znowu dzwonił.
That guy who was here yesterday called again. (informal co for który)
Second — and this is standard in every register — co is the relative pronoun when the antecedent is a whole clause or an indefinite pronoun like to, wszystko, coś, nic. Here co itself declines (co / czego / czemu / czym) according to its role:
Zrobił wszystko, co mógł.
He did everything (that) he could.
To, czego się nauczyłeś, zostanie z tobą na zawsze.
What you've learned will stay with you forever. (czego — genitive after nauczyć się)
Spóźnił się, co nikogo nie zdziwiło.
He was late, which surprised no one. (co referring to the whole previous clause)
Common Mistakes
❌ Książka który czytam jest ciekawa.
Incorrect — missing comma, and który doesn't agree with the feminine antecedent.
✅ Książka, którą czytam, jest ciekawa.
The book I'm reading is interesting.
Two errors at once: no comma, and który not matched to feminine książka (→ którą) in the accusative.
❌ To kobieta, który widziałem wczoraj.
Incorrect — the antecedent is feminine, so the form must be która, accusative którą.
✅ To kobieta, którą widziałem wczoraj.
That's the woman I saw yesterday.
The gender comes from the antecedent kobieta (feminine) → którą; the accusative comes from being the object of widziałem.
❌ Dom, który mieszkam, jest stary.
Incorrect — 'live in' needs the preposition w + locative, so it must be w którym.
✅ Dom, w którym mieszkam, jest stary.
The house I live in is old.
You can't drop the preposition the way English drops "in". Mieszkać requires w + locative, so the relative must be w którym.
❌ Wszystko, które wiem, jest tutaj.
Incorrect — after wszystko the relative pronoun is co, not które.
✅ Wszystko, co wiem, jest tutaj.
Everything I know is here.
Indefinite antecedents (wszystko, to, coś, nic) take relative co.
❌ Koleżanka, z który pracuję, jest miła.
Incorrect — feminine antecedent plus z (instrumental) gives z którą.
✅ Koleżanka, z którą pracuję, jest miła.
The colleague I work with is nice.
Feminine koleżanka fixes the stem (która); the preposition z fixes the case (instrumental którą). The preposition leads the clause.
Key Takeaways
- który agrees in gender and number with its antecedent but takes its case from its role in the relative clause — "gender from behind, case from ahead."
- A comma always precedes który (and any relative clause); Polish has no restrictive/non-restrictive comma choice.
- Plural splits into którzy (groups with a male person) vs. które (everything else).
- jaki/taki express the kind that; co is the relative for wszystko, to, coś, nic and for whole clauses, and an informal substitute for który in speech.
- The preposition always sits in front of który — Polish never strands prepositions at clause end.
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Start learning Polish→Related Topics
- Relative Clauses with któryB1 — How to build Polish relative clauses with który — agreeing in gender and number with the antecedent but taking its case from its own clause — plus the obligatory comma and the ban on stranded prepositions.
- Punctuation and the CommaA2 — How Polish punctuation differs from English — above all the strict, grammar-driven comma before subordinate clauses.
- Verb Government: Which Case a Verb TakesB1 — Which case a Polish verb demands for its object — a categorized overview of accusative, genitive, dative, instrumental, and prepositional government, with the insight that the Polish case rarely matches the English preposition.
- which, what kind, whose: który, jaki, czyjB1 — How Polish splits English 'what/which' into który (selecting from a set) and jaki (asking about quality or kind), plus the dedicated possessive question word czyj ('whose').
- Interrogative Pronouns: kto, coA1 — The question words kto 'who' and co 'what' fully decline — the case you choose telegraphs how the answer fits into the sentence, and kto always triggers masculine agreement.