English lets a single which or that introduce almost any relative clause. Finnish splits the job in two: joka attaches to a concrete noun it refers back to, while mikä refers back to a whole clause, to an indefinite or superlative head, or to the pronoun se. Pick the wrong one and the sentence reads as broken to a native ear. This page is the decision rule; for building the clause itself (word order, case of the pronoun) see relative clauses.
The one decision: a noun, or something bigger?
- joka → the relative refers to one specific noun just named (a house, a man, a book).
- mikä → the relative refers to a whole idea — an entire clause, an indefinite word like kaikki ("everything"), a superlative like paras ("the best"), or the bare pronoun se.
Talo, joka on tuolla, on vanha.
The house that is over there is old. (joka — refers to the noun 'talo')
Osta se, mikä on halvin.
Buy the one that is cheapest. (mikä — refers to the pronoun se + superlative)
The core case — a named noun as the antecedent — is always joka. Reach for mikä only when there is no single noun to point at.
Nainen, joka asuu yläkerrassa, soittaa pianoa.
The woman who lives upstairs plays the piano. (noun antecedent → joka)
joka declines for its job inside the clause
joka takes whatever case its role demands inside the relative clause, not the case of the noun it refers to. So "the man whom I saw" needs the object form, "the house in which we lived" needs the inessive, and so on. The stem is jo-.
| Role in the clause | Form | Example fragment |
|---|---|---|
| Subject (who / which) | joka | mies, joka nauraa |
| Genitive (whose) | jonka | mies, jonka auto… |
| Object (whom / which) | jonka / jota | kirja, jonka luin |
| Inessive (in which) | jossa | talo, jossa asuin |
| Adessive (with / by which) | jolla | auto, jolla ajoin |
Kirja, jonka ostin eilen, on jo luettu.
The book (that) I bought yesterday is already read. (jonka — object of ostin)
Mies, jota odotin, ei koskaan tullut.
The man (whom) I was waiting for never came. (jota — partitive object of odottaa, which always governs the partitive)
Talo, jossa asuimme lapsena, on nyt purettu.
The house we lived in as children has now been demolished. (jossa — inessive)
One habit English speakers must unlearn: English happily drops the relative word — "the book I read," "the man I saw" — but Finnish never can. The pronoun always has to be there, in the case its role demands. "The book I read" is kirja, *jonka luin — with *jonka obligatory and spelled out.
Ruoka, jonka tilasin, oli kylmää.
The food I ordered was cold. (English drops 'that'; Finnish keeps jonka)
When you need mikä instead
Use mikä in three named situations. There is no way to derive them from a general rule other than "there's no single noun to grab onto," so learn the triggers:
1. After an indefinite pronoun — kaikki (everything/all), jokin (something), mikään (anything):
Kaikki, mikä kiiltää, ei ole kultaa.
All that glitters is not gold. (mikä after kaikki)
2. After a superlative or a "the only" head — paras, ainoa, ensimmäinen:
Se oli paras päätös, minkä olen tehnyt.
That was the best decision I've ever made. (minkä after superlative paras)
3. Referring back to a whole preceding clause — where English uses ", which…":
Hän saapui ajoissa, mikä yllätti kaikki.
He arrived on time, which surprised everyone. (mikä = the whole fact that he arrived on time)
Common Mistakes
❌ Talo, mikä on vanha, myytiin.
A concrete noun antecedent takes joka, never mikä.
✅ Talo, joka on vanha, myytiin.
The house that is old was sold.
❌ Hän myöhästyi, joka oli harmi.
Here 'which' refers to the whole clause (his being late), so mikä, not joka.
✅ Hän myöhästyi, mikä oli harmi.
He was late, which was a pity.
❌ Kaikki, joka on tärkeää, on tallessa.
After the indefinite kaikki the relative is mikä.
✅ Kaikki, mikä on tärkeää, on tallessa.
Everything that matters is safe.
❌ Mies, joka näin, oli tuttu.
joka is the subject form; as the object of näin you need jonka.
✅ Mies, jonka näin, oli tuttu.
The man (whom) I saw was familiar.
❌ Se oli paras elokuva, joka olen nähnyt.
After the superlative paras the relative is mikä (here minkä as object).
✅ Se oli paras elokuva, minkä olen nähnyt.
That was the best film I've ever seen.
Key Takeaways
- joka refers back to a specific named noun; mikä refers to a clause, an indefinite/superlative head, or se.
- joka takes the case its role demands inside the clause: jonka (object/genitive), jota (partitive object), jossa (in which), jolla (with which).
- Three fixed mikä triggers: after kaikki/jokin/mikään, after paras/ainoa/ensimmäinen, and after a whole preceding clause (English ", which…").
- English which/that collapses both — never carry that habit over to a concrete noun: talo, *joka on vanha, not
talo, mikä*. - Watch the look-alike: relative joka ≠ the quantifier joka ("every," as in joka päivä).
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Start learning Finnish→Related Topics
- The Relative Pronoun jokaB1 — joka links a relative clause to a specific noun — agreeing with it in number but taking the case its own clause demands (jonka, jota, jossa, jolle).
- Relative mikä and Its UsesB2 — When the antecedent is a whole clause, a pronoun like se or kaikki, or a superlative, the relative is mikä — not joka. The rule and its cases.
- Relative Clauses with joka and mikäB2 — Finnish relative clauses use joka for a specific noun and mikä for a clause, a pronoun or a superlative. joka takes its case from its role inside the clause.
- mikä vs kukaA2 — Which question word to use: kuka asks who (a person's identity), mikä asks what or which (a thing, a kind, or a name) — plus their case forms and the trap of asking *Mikä hän on?