Two of the commonest Finnish question words split "who" from "what" along a line English also draws — but Finnish holds that line strictly, and it punishes crossing it. kuka asks about a person's identity; mikä asks about a thing, a kind, or a name. This page is the decision rule and the case forms you need to ask real questions; for the wider set of question words see the interrogatives page.
The one decision: a person, or a thing?
- kuka → who — you want to know which person it is (their name, their identity).
- mikä → what / which — you want to know what kind of thing it is, or its name as a label.
Kuka hän on?
Who is she? (asking for the person's identity)
Mikä tämä on?
What is this? (asking what the thing is)
That looks easy until you notice the danger zone: asking about a person with mikä. It is grammatical, but it changes the meaning entirely — you are no longer asking who they are, you are asking what they are.
Mikä hän on? — Hän on opettaja.
What is she? — She's a teacher. (mikä about a person asks profession/category, not identity)
The name trap: "What's your name?" uses mikä
Here is the counter-intuitive corner that catches almost every learner. Asking someone's name is done with mikä, not kuka — because you are not asking which person is standing here (you can see that), you are asking for a label, and a name is a thing.
Mikä sinun nimesi on?
What's your name? (a name is a label → mikä, not kuka)
Kuka sinä olet?
Who are you? (asking identity/role — a different, blunter question)
Both are grammatical, but they aren't interchangeable: Mikä sinun nimesi on? politely asks the name, while Kuka sinä olet? challenges the whole identity ("and who are you?"). Reaching for Kuka sinun nimesi on? — "who is your name?" — is a dead giveaway of an English speaker.
Both decline — and kuka changes its whole stem
You rarely use these words in the bare nominative alone. To ask whose, whom, to whom you inflect them. mikä inflects predictably off mi-, but kuka is irregular: every case except the nominative is built on a different stem, kene-.
| Meaning | kuka (who) | mikä (what / which) |
|---|---|---|
| Nominative | kuka | mikä |
| Genitive (whose / of what) | kenen | minkä |
| Partitive (whom / what, object) | ketä | mitä |
| Adessive (on whom / with what) | kenellä | millä |
| Allative (to whom) | kenelle | mille |
| Accusative (whom, total object) | kenet | — |
Kenen takki tämä on?
Whose coat is this? (kenen — genitive of kuka)
Ketä sinä etsit?
Who(m) are you looking for? (ketä — partitive of kuka)
Kenelle sinä kirjoitat?
Who are you writing to? (kenelle — allative of kuka)
mikä + noun = "which"; mitä = "what" as an object
mikä placed in front of a noun turns into English which: you're choosing one item out of a known set.
Mikä juna menee Turkuun?
Which train goes to Turku? (mikä + noun = which)
Mihin aikaan tapaamme?
At what time shall we meet? (mihin = illative of mikä, 'to what')
As a bare object, what is normally the partitive mitä, because questioned objects are typically partitive.
Mitä sinä sanoit?
What did you say? (mitä — partitive object)
Mitä te teette viikonloppuna?
What are you doing at the weekend?
The idiom you'll hear on day one
Mitä kuuluu? literally asks "what is heard / what belongs?" but functions as How are you? It's fixed — you can't swap in kuka or rebuild it — so just learn it whole.
Moi! Mitä kuuluu? — Kiitos hyvää!
Hi! How are you? — I'm well, thanks! (a fixed greeting)
Common Mistakes
❌ Mikä hän on? (meaning: who is she?)
This asks her profession/category, not her identity — for 'who' use kuka.
✅ Kuka hän on?
Who is she?
❌ Kuka tämä on? (pointing at an object)
An object isn't a person — asking what a thing is needs mikä.
✅ Mikä tämä on?
What is this?
❌ Kukan auto tämä on?
No such form — the genitive of kuka is built on the kene- stem.
✅ Kenen auto tämä on?
Whose car is this?
❌ Mikä sinä etsit?
You're looking for a person, and it's an object — use the partitive ketä.
✅ Ketä sinä etsit?
Who(m) are you looking for?
❌ Kuka sinun nimesi on?
A name is a label, not a person — asking for it uses mikä.
✅ Mikä sinun nimesi on?
What's your name?
❌ Mikä kuuluu?
The greeting is fixed as Mitä kuuluu? — the partitive mitä can't be swapped for the nominative.
✅ Mitä kuuluu?
How are you?
Key Takeaways
- kuka = who (a person's identity, answered by a name); mikä = what / which (a thing, kind, or name).
- Asking Mikä hän on? is legal but means "what is she" — her job or category, not who she is.
- kuka switches to the kene- stem in every non-nominative case: kenen, ketä, kenellä, kenelle, kenet.
- mikä + noun = which; bare object what = the partitive mitä; for two options prefer kumpi.
- The greeting Mitä kuuluu? ("How are you?") is a fixed idiom — memorise it whole.
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Start learning Finnish→Related Topics
- Question Pronouns: kuka, mikä, kumpi, millainenA1 — Finnish question words for who, what/which, which-of-two, and what-kind — with their suppletive case forms kenen, minkä and kumman.
- Question Words: kuka, mikä, missä, milloin, miksiA1 — Finnish open questions use pro-words with no -ko: kuka, mikä, the place trio missä/mistä/mihin, milloin and miksi — and kuka and mikä decline.
- joka vs mikä (Relative)B1 — Choosing the relative pronoun: joka points back to a specific noun antecedent, while mikä points back to a whole clause, an indefinite or superlative head, or the pronoun se.
- Declining Personal Pronouns: minä → minua → minutA2 — The case forms of Finnish personal pronouns — genitive minun, partitive minua, the special accusative minut, and the local cases minulla, minulle.