Learn Hardcore Finnish: Kun tulen kotiin, riisun takin eteisessä. - When I come home, I take off my coat in the hallway.

You can say Kun minä tulen kotiin, minä riisun takin eteisessä, but it usually sounds heavy or emphatic. The neutral everyday version leaves minä out, as in the example sentence.

What exactly does kun mean here, and how is it different from jos or milloin?

In this sentence kun means when in the sense of at the time that.

Kun tulen kotiin… = When I come home… (fact / whenever this happens)

Contrast with:

jos tulen kotiin… = if I come home… (uncertain; maybe I come home, maybe not)
milloin tulen kotiin… = when I come home… but usually used in questions like Milloin tulen kotiin? = When will I come home?

So kun introduces a time clause, not a conditional or a question.

Why is there a comma after Kun tulen kotiin?

In Finnish, a subordinate clause that comes before the main clause is normally separated by a comma.

Kun tulen kotiin, = subordinate clause
riisun takin eteisessä. = main clause

This is mostly a punctuation rule: when a clause starts with words like kun, koska, vaikka, jos, etc., and comes first, you put a comma before the main clause.

Does tulen express present or future time? Could it mean “When I get home, I will…”?

Finnish does not have a separate future tense. The present tense is used for:

present: When I (usually) come home…
near future: When I get home (later today)…

So Kun tulen kotiin, riisun takin eteisessä can mean both:

When I come home, I (normally) take off my coat in the hallway. (habit)
When I get home, I’ll take off my coat in the hallway. (future plan)

Context decides which one is meant.

Why is it kotiin and not just koti or kotona?

These are different cases with different meanings:

koti = home (basic form, used mostly in compounds or with certain verbs)
kotiin = to(wards) home – illative case (movement to a place)
kotona = at home – adessive/inesthetic meaning “at/in a place”

In the sentence we have motion towards home:

tulen kotiin = I come (to) home / I get home

If you said tulen kotona, it would be wrong, because kotona describes a location, not a direction of movement.

What does riisun mean exactly, and why that verb instead of something with ottaa?

riisun is the 1st person singular of riisua, which specifically means to take off (clothes, shoes, etc.).

riisun takin = I take off (my) coat.

You could also say otan takin pois (I take the coat off), but riisua is the standard, concise verb for removing clothing. English needs two words (“take off”), but Finnish has a single verb.

Why is it takin and not takki or takkia?

takki (coat) is inflected here as a total object, because you remove the whole coat once, as a complete event.

Key forms:

takki = nominative (a coat; also used as total object in some contexts)
takin = genitive/accusative singular, here functioning as total object
takkia = partitive singular, typically for incomplete/ongoing actions or “some (of) a thing”

In finite, bounded actions like take off the whole coat, Finnish usually uses a total object form (takin). Compare:

Syön omenan. = I eat the apple (all of it). → omenan (total)
Syön omenaa. = I am (in the middle of) eating an apple / some apple. → omenaa (partitive)

So riisun takin = you perform the whole action on the whole coat.

What does eteisessä mean exactly, and what case is it in?

eteisessä is the inessive form of eteinen (hall, entryway).

eteinen = the entry hall, hallway (by the front door)
eteisessä = in the hallway (inside that space)

The inessive case (-ssa/ssä) usually corresponds to English in or inside:

talossa = in the house
autossa = in the car
eteisessä = in the hallway / in the entry

So riisun takin eteisessä = I take off my coat in the hallway.

Could I say eteiseen or eteisestä instead of eteisessä?

They mean different directions:

eteiseen (illative) = into the hallway (movement into)
eteisessä (inessive) = in the hallway (location inside)
eteisestä (elative) = from the hallway (movement out of)

In the sentence there is no movement described for the hallway; you’re just saying where you remove the coat. So eteisessä (location) is correct.

If you wanted to describe your movement as well, you could say for example:

Menin eteiseen ja riisuin takin. = I went into the hallway and took off my coat.

Can I change the word order and say Riisun takin eteisessä, kun tulen kotiin?

Yes, that is grammatically correct. Finnish word order is relatively flexible.

Kun tulen kotiin, riisun takin eteisessä.
Riisun takin eteisessä, kun tulen kotiin.

Both can mean the same thing. The difference is a slight change in emphasis:

Original order puts more focus on the time condition (“When I come home…”).
The alternative starts from what you do (“I take off my coat in the hallway, when I come home”).

In neutral context, both are fine.

Is kotiin like “to the home” or “to my home”? Where are the articles and possessives?

Finnish has no articles (a, an, the), so kotiin simply means to home, and context specifies whose home it is. In everyday speech, kotiin usually implies to my/our home if you are talking about yourself.

If you wanted to be explicit about whose home, you would use other structures, for example:

menen hänen kotiinsa = I go to his/her home
menen ystäväni kotiin = I go to my friend’s home

How would I make it even more clearly “When I get home, I will take off my coat in the hallway” (future plan)?

Usually the original present tense is enough:

Kun tulen kotiin, riisun takin eteisessä.

If you really want to stress the future or intention, you can add an adverb or phrase:

Kun tulen kotiin, aion riisua takin eteisessä.
= When I get home, I intend to take off my coat in the hallway.

But in normal conversation, the plain present is the most natural choice, and it is understood as future if the context is future.