Learn Hardcore Finnish: Vaatekaappi on niin täynnä, että kumpikaan ovi ei mene kiinni. - The wardrobe is so full that neither door closes.

It’s a result construction meaning so ... that .... Niin intensifies the adjective/adverb (niin täynnä = so full), and että introduces the consequence. Finnish normally places a comma before että, so the comma is required.

Why is täynnä used instead of täysi?

Both can be correct, but they behave a bit differently:

täynnä is the common predicative form meaning “full (of something)” and often takes a partitive complement: vaatekaappi on täynnä vaatteita.
täysi is an adjective meaning “full, complete,” used attributively (täysi kaappi) or predicatively with a slightly more absolute feel: kaappi on täysi (= completely full). In everyday speech about containers, täynnä is more typical.

Can I specify what the wardrobe is full of?

Yes, use the partitive after täynnä: Vaatekaappi on niin täynnä vaatteita, että kumpikaan ovi ei mene kiinni.

What exactly does kumpikaan mean?

Kumpikaan refers to one of two items and is typically used with negation to mean “neither (one).” In positive contexts it can mean “either (one),” but that use is rare; you’d usually say kumpi tahansa for “either/whichever of the two.”

Why is it singular kumpikaan ovi and ei mene, not plural?

Because kumpikaan is grammatically singular. The verb agrees: kumpikaan ovi ei mene. If you want a plural subject, use kummatkaan: Kummatkaan ovet eivät mene kiinni.

What does mene kiinni literally mean? Why not use a verb like “close”?

Mennä kiinni is a very common intransitive idiom meaning “to close/shut (by itself).” Alternatives:

ei sulkeudu = doesn’t close (intransitive)
ei pysy kiinni = won’t stay closed (different nuance: it closes but won’t remain shut)
Transitive: sulkea = to close something: En saa ovea suljettua.

Why is there a comma before että?

Finnish places a comma before most subordinate clauses, including että-clauses. So ..., että ... is standard punctuation.

Can I write ettei instead of että ei?

Yes. Ettei is the fused form of että ei. Your clause can be: Vaatekaappi on niin täynnä, ettei kumpikaan ovi mene kiinni. For plural: etteivät (e.g., etteivät ovet mene).

Does niin here just mean “very”?

Not on its own. In niin ... että, niin is part of the fixed “so ... that ...” pattern. If you simply mean “very full,” you’d use todella/erittäin täynnä without an että-clause.

How would I say “too full for the doors to close”?

Use liian ... jotta with the conditional: Vaatekaappi on liian täynnä, jotta ovet menisivät kiinni. (You can also keep the “two doors” nuance: ..., jotta kumpikaan ovi ei menisi kiinni.)

What is kiinni exactly?

It’s an adverb meaning “closed, shut; attached.” Common patterns:

Ovi on kiinni (the door is closed)
Ovi menee kiinni (the door closes)
Pane ovi kiinni / Laita ovi kiinni (shut the door)
Ovi pysyy kiinni (the door stays closed)

Are there any case endings in the sentence?

The nouns vaatekaappi and ovi are in the nominative (subjects). Täynnä is an invariant predicative form (historically an essive). Kiinni is an adverb. The negation ei mene uses the connegative verb form mene.

Why not say vaatekaapissa (in the wardrobe) somewhere?

Here the wardrobe itself is the subject that’s full: Vaatekaappi on täynnä. You’d use vaatekaapissa (inessive) if you were talking about something located inside it: Vaatekaapissa on paljon vaatteita.

Why is it ei mene and not ei menee?

Finnish negation uses the negative auxiliary (en, et, ei, emme, ette, eivät) plus the connegative base of the main verb. So present tense is ei mene (not ei menee). Affirmative would be menee.

Could I change the word order or structure?

Yes, for example:

Kumpikaan ovi ei mene kiinni, koska vaatekaappi on niin täynnä. (states the reason with koska)
Vaatekaappi on niin täynnä vaatteita, ettei ovet mene kiinni. (plural version) All these are natural, with small differences in emphasis.

Is there a difference between kumpi, kumpikin, and kumpikaan?

kumpi = which (of two): Kumpi ovi?
kumpikin = both (of the two): Kumpikin ovi menee kiinni.
kumpikaan = either/neither (of two), usually with negation: Kumpikaan ovi ei mene kiinni.

Any pronunciation or spelling gotchas?

Yes: kiinni has double vowels and a double consonant: k-i-i-n-n-i. Length matters in Finnish: kiini or kini would be wrong. Also, gemination affects rhythm: [kíi-nni].