Learn Hardcore Finnish: Pöytä on kahden tuolin välissä, ja opettaja istuu edessä. - The table is between two chairs, and the teacher sits in front.

Because the postposition välissä (“between”) requires its complement in the genitive. When a numeral phrase is put into the genitive, both the numeral and the noun take genitive singular: kahden tuolin. The bare form kaksi tuolia is the nominative/accusative phrase (“two chairs”) used as a subject or object, not as a genitive complement.

Why is tuolin singular if we mean two chairs? Shouldn’t it be plural (tuolien)?

With numerals 2 and higher, Finnish treats the counted noun as singular inside case-marked numeral phrases. So you get:

NOM: kaksi tuolia (“two chairs”)
GEN: kahden tuolin (“of two chairs”)
ILL: kahteen tuoliin (“into two chairs”)
ADE: kahdella tuolilla (“on two chairs”) Genitive plural (tuolien) is used when there’s no numeral: e.g. tuolien välissä “between the chairs (in general).”

What exactly is välissä—a case ending or a preposition?

It’s a postposition built from the noun väli (“gap/space”) in the inessive case. As a postposition it takes a genitive complement: [GEN] + välissä = “between X.” Its full local-case series:

direction to: väliin (“into the space between”)
location in: välissä (“in the space between”)
direction from: välistä (“out from between”)

What’s the difference between välissä and välillä?

välissä: physically “in the gap/space between,” often with concrete objects close together. Here: Pöytä on kahden tuolin välissä is the natural choice.
välillä: “between” in a looser or more abstract sense—routes, times, ranges, or areas: Juna kulkee Helsingin ja Turun välillä (“The train runs between Helsinki and Turku”). It can also be used for areas between larger objects, but for two chairs the “in the gap” nuance of välissä fits best.

Where’s the “of what” after edessä? Doesn’t edessä need a complement?

Often it does: [GEN] + edessä = “in front of X,” e.g. pöydän edessä, talon edessä, minun edessäni. But edessä can also be used adverbially to mean “at/in the front” when the reference point is obvious (e.g., a classroom or hall). So opettaja istuu edessä ≈ “the teacher sits at the front.”

How do I say “in front of the table”?

Pöydän edessä. For example: Opettaja istuu pöydän edessä.

What are the “movement vs. location” forms for edessä and välissä?

Front:
- to the front: eteen
- at/in front: edessä
- from in front: edestä
Between:
- into between: väliin
- in between: välissä
- out from between: välistä Use the “to/at/from” contrast to match motion vs. static location.

Why is istuu translated as “is sitting” even though there’s no -ing?

Finnish has no separate present progressive. The simple present istuu covers both “sits” and “is sitting.” Context decides the best English rendering.

Is the comma before ja correct here?

Yes. Finnish normally uses a comma between two independent main clauses even when joined by ja, especially when the subjects differ:

Pöytä on …, ja opettaja istuu … No comma when the clauses share a subject or form one predicate: Menin kauppaan ja ostin maitoa.

Can I change the word order?

Yes. Case-marking allows flexibility. For example:

Kahden tuolin välissä on pöytä.
Opettaja istuu edessä (unchanged), or with an explicit reference point: Opettaja istuu luokan edessä. Changing order shifts emphasis but keeps the meaning.

How would I say “between these two chairs” vs. just “between two chairs”?

Add a demonstrative for specificity:

“between two chairs” (any): kahden tuolin välissä
“between these two chairs”: näiden kahden tuolin välissä

Could I say tuolien välissä instead of kahden tuolin välissä?

You can, but it changes the meaning:

kahden tuolin välissä = specifically between two chairs
tuolien välissä = “between the chairs” (non-specific set of chairs)

Why on and not olla or oli?

On is the 3rd person singular present of olla (“to be”). Olla is the infinitive; oli is the past (“was”).

How do I say “in front of us” and “between us”?

With pronouns, use the genitive pronoun plus the postposition, typically with a possessive suffix:

“in front of us”: meidän edessämme (you can also say simply edessämme)
“between us”: meidän välissämme (also välissämme)

Is there any article-like way to mark “a table” vs. “the table”?

Finnish has no articles. Pöytä can mean “a table” or “the table.” Use context or demonstratives for specificity: se pöytä (“that/the table”), tämä pöytä (“this table”).

Can I say opettaja istuu eteen to mean “the teacher sits in the front”?

No. Eteen indicates motion (“to the front”). With the stative verb istua use the location form: opettaja istuu edessä. If describing movement, use a motion verb: opettaja menee luokan eteen (“the teacher goes to the front of the class”).