Learn Hardcore Finnish: Minä pysäköin auton talon taakse.

Finnish often uses the -n form (same as genitive) for a total object: the action is seen as complete and affecting the whole thing.
Minä pysäköin auton = I (completely) park(ed) the car (the parking is done, the whole car is parked).

Other possibilities:

auto (nominative) as object appears mainly in plural or with certain structures.
autoa (partitive) would suggest an ongoing, incomplete, or repeated action, or some other special nuance (see a later question on autoa).

Is auton genitive or accusative here, and does that matter?

Formally, auton looks like genitive singular, but in this sentence it functions as the accusative object.

For most nouns, the accusative singular is identical in form to the genitive (-n).
So grammarians may call it accusative (because of its function) or genitive (because of its form.

For learning purposes, you can remember:

When a direct object of a completed action ends in -n, it’s the “total object” form (accusative), even though it looks like genitive.

Why is talon also in the -n form? Is it another object?

No, talon is not another object. Here it is a genitive complement of the postposition taakse.

Structure: talon taakse = to behind the house / behind the house (direction towards)
Many Finnish postpositions (like takana, taakse, takaa, etc.) take their complement in the genitive:
- talon takana = behind the house (location)
- talon taakse = (to) behind the house (movement to that place)
- talon takaa = from behind the house (movement from that place)

So:

auton = object
talon = genitive word that tells whose / which back we are talking about (the back of the house).

Why do we say talon taakse and not talon takana?

Because the sentence expresses movement to a place, not staying at a place.

talon taakse uses taakse, which is the directional form (“to behind”).
talon takana uses takana, which is the static location form (“at behind”).

Compare:

Auto on talon takana. = The car is behind the house. (static location)
Minä pysäköin auton talon taakse. = I park(ed) the car behind the house. (movement to that location)

What exactly is taakse? A case ending or a separate word?

Taakse is a separate word, a postposition derived from the noun taka (back).

There is a three-way pattern:

takana = at the back / behind (static)
taakse = to the back / behind (movement to)
takaa = from the back / from behind (movement from)

With a noun in genitive:

talon takana = behind the house (location)
talon taakse = to behind the house (destination)
talon takaa = from behind the house (origin)

So talon taakse is a postpositional phrase (“to behind the house”), not a single word with a case ending attached to talo.

Why does pysäköin end in -n?

The -n marks first person singular (I) on the verb.

Verb: pysäköidä = to park
Stem: pysäköi-
minä pysäköin = I park / I parked
sinä pysäköit = you park / parked
hän pysäköi = he/she parks / parked

So the -n tells you the subject is “I”, and that’s why Minä can be dropped: Pysäköin auton… is still clearly “I park(ed) the car…”.

How do I know if pysäköin is present or past tense?

In this particular verb type, minä pysäköin is the same form in both present and past.

It can mean:
- I park the car behind the house. (present)
- I parked the car behind the house. (past)

Finnish usually relies on context or time expressions:

Eilen pysäköin auton talon taakse. = Yesterday I parked the car behind the house. (clearly past)
Yleensä pysäköin auton talon taakse. = I usually park the car behind the house. (habitual present)

So you need context to distinguish present vs past here.

Can I leave out Minä?

Yes, and that is very common and natural.

Minä pysäköin auton talon taakse.
Pysäköin auton talon taakse.

Both mean “I park(ed) the car behind the house.”

Because the verb ending -n already encodes “I”, the subject pronoun Minä is only needed for:

emphasis (e.g. I did it, not someone else)
clarity in contrastive contexts.

Can I change the word order, like Pysäköin auton talon taakse or Auton pysäköin talon taakse?

Yes. Finnish word order is flexible, and changes usually affect emphasis more than basic meaning.

All of these are grammatically correct:

Minä pysäköin auton talon taakse. (neutral, subject–verb–object)
Pysäköin auton talon taakse. (neutral without pronoun)
Auton pysäköin talon taakse. (emphasis on auton – It’s the car that I park behind the house)
Talon taakse pysäköin auton. (emphasis on where you park it)

For a beginner, the safest default is:

(Minä) pysäköin auton talon taakse.

When would I use autoa instead of auton with pysäköidä?

You use autoa (partitive) when the action is seen as ongoing, incomplete, or not affecting the whole thing, or in some special contexts.

Examples:

Ongoing / in-progress action
- Pysäköin autoa, kun hän soitti.
  = I was parking the car when he/she called.
  The parking isn’t viewed as a completed whole event at that moment.
Negation
- En pysäköi autoa talon taakse.
  = I don’t park the car behind the house.
  Negated objects in Finnish are partitive.
Unbounded / repeated action without clear totality (context can push towards partitive)

In contrast, auton presents it as a complete event: the car ends up parked.

How would I say “I parked the car behind the house” vs “I park the car behind the house (every day)”? Is the sentence the same?

Yes, the form can be the same; context supplies the time frame.

Pysäköin auton talon taakse.
- With a past-time adverbial (e.g. eilen, aamulla), it means “I parked the car…”
- With a habitual adverbial (e.g. yleensä, aina, joka päivä), it means “I (usually) park the car…”

Examples:

Eilen pysäköin auton talon taakse. = Yesterday I parked the car behind the house.
Joka päivä pysäköin auton talon taakse. = Every day I park the car behind the house.

So written or spoken alone, Pysäköin auton talon taakse is tense-ambiguous; context clarifies it.

How would I say “behind my house” or “behind that house” using this structure?

You keep the same pattern ([noun in genitive] + taakse) and change the noun:

minun taloni taakse = behind my house (movement)
- Full sentence: Pysäköin auton minun taloni taakse.
- More natural: Pysäköin auton taloni taakse. (possessive suffix is enough; minun can be dropped)
sen talon taakse = behind that house (movement)
- Pysäköin auton sen talon taakse.

For location (no movement), you’d use takana instead of taakse:

taloni takana = behind my house
sen talon takana = behind that house

Is talon taakse like a prepositional phrase in English?

Functionally, yes, but grammatically it’s a postpositional phrase.

In English: behind the house (preposition before the noun)
In Finnish: talon taakse (postposition after the noun)

Pattern:

Noun in genitive
- postposition:
  - talon taakse = (to) behind the house
  - talon takana = behind the house (location)
  - talon takaa = from behind the house

So you can think of talon taakse as the Finnish equivalent of an English prepositional phrase, but with the “preposition” placed after the noun.