Learn Hardcore Finnish: Bussi ajaa pysäkin ohi.

ajaa is the standard verb when a vehicle is the subject.
English usually says go with a vehicle, but Finnish prefers ajaa for things like buses, cars, trams, etc.

What are the grammatical roles of bussi, ajaa, pysäkin, and ohi?

bussi – subject, nominative singular
ajaa – verb, 3rd person singular present of ajaa
pysäkin – genitive singular of pysäkki (“stop”)
ohi – postposition/adverb meaning “past, by, over”

Structure:

Bussi (who/what?) → subject
ajaa (does what?) → verb
pysäkin ohi (in what way / where relative to something?) → adverbial phrase meaning “past the stop”

The key pattern is:

ajaa + GENITIVE + ohi = “drive/go past X”
- auto ajaa talon ohi – the car goes past the house
- juna menee aseman ohi – the train goes past the station

Why is it pysäkin (genitive) and not pysäkki or some other case?

Some Finnish postpositions (words like ohi, kanssa, luona, etc.) require the noun before them to be in the genitive case.

The pattern is:

GENITIVE + ohi
- pysäkin ohi – past the stop
- talon ohi – past the house
- kaupungin ohi – past the city

So:

pysäkki ohi – incorrect
pysäkin ohi – correct

You don’t use partitive or other cases here; ohi specifically takes the genitive object it refers to.

What exactly is ohi? Is it a preposition, an adverb, or something else?

Ohi is traditionally classified as a postposition, but it also behaves very much like an adverb.

As a postposition, it follows a genitive noun:

pysäkin ohi – past the stop
talon ohi – past the house

As a more general adverb, it can mean things like:

Se on ohi. – It is over / It’s finished.
Peli on ohi. – The game is over.

So in Bussi ajaa pysäkin ohi, ohi is a postposition that tells you the movement is past the stop.

Can you change the word order? For example, is Bussi ajaa ohi pysäkin possible?

The normal, neutral word order is:

Bussi ajaa pysäkin ohi.

The noun + ohi form a tight phrase, and usually the noun comes before ohi:

pysäkin ohi – past the stop (most natural)

Bussi ajaa ohi pysäkin sounds odd or at least very marked; it breaks up the postpositional phrase.

If you want to change the order for emphasis or topic, you usually move the whole phrase:

Pysäkin ohi bussi ajaa. – It’s past the stop that the bus goes. (emphasis on pysäkin ohi)

But for basic, everyday speech: Bussi ajaa pysäkin ohi is the standard form.

How do I say this in the past tense: “The bus went past the stop”?

You just put ajaa into the past tense (ajoi):

Bussi ajoi pysäkin ohi. – The bus went / drove past the stop.

Mini conjugation of ajaa (singular persons, indicative):

minä ajan – I drive
sinä ajat – you drive
hän ajaa – he/she drives
minä ajoin – I drove
sinä ajoit – you drove
hän ajoi – he/she drove

So you can also say:

Ajan pysäkin ohi. – I drive past the stop.
Ajoin pysäkin ohi. – I drove past the stop. (I missed the stop.)

How do I make this negative, like “The bus does not go past the stop”?

Use the negative verb ei and the verb stem aja-:

Bussi ei aja pysäkin ohi. – The bus does not go past the stop.

Pattern:

Bussi ajaa pysäkin ohi. – The bus goes past the stop.
Bussi ei aja pysäkin ohi. – The bus does not go past the stop.

If you want past negative:

Bussi ei ajanut pysäkin ohi. – The bus did not go past the stop.

What is the difference between Bussi ajaa pysäkin ohi and Bussi menee pysäkin ohi?

Both are possible and understandable, but:

ajaa – specifically about driving vehicles (cars, buses, trams, etc.)
mennä – a very general verb “to go”

So:

Bussi ajaa pysäkin ohi. – Most natural, emphasizes the bus as a driven vehicle.
Bussi menee pysäkin ohi. – Also OK, but stylistically more neutral/generic: “the bus goes past the stop.”

In everyday speech, ajaa feels particularly appropriate for buses, cars, trams; mennä is more widely used with people, animals, and abstract things.

In English the driver drives the bus. Can I say something like “The driver drives past the stop” in Finnish?

Yes. Then the driver becomes the subject:

Kuljettaja ajaa pysäkin ohi. – The driver drives past the stop.
Bussinkuljettaja ajaa pysäkin ohi. – The bus driver drives past the stop.

Both structures are natural:

Bussi ajaa pysäkin ohi. – The bus goes past the stop.
Kuljettaja ajaa pysäkin ohi. – The driver drives past the stop.

Finnish easily uses a vehicle as the subject of ajaa, where English would often prefer “go” or make the driver the subject.

Why isn’t there any word for “the” in bussi or pysäkin?

Finnish has no articles (no a/an and no the).

Definiteness or indefiniteness is understood from:

context
word order
pronouns, if needed

So:

Bussi ajaa pysäkin ohi.
- can mean “A bus goes past the stop”
- or “The bus goes past the stop”, depending on context.

If you really need to specify which bus, you can add more information:

Se bussi ajaa pysäkin ohi. – That bus goes past the stop.
Tämä bussi ajaa pysäkin ohi. – This bus goes past the stop.

Can I drop pysäkin and just say Bussi ajaa ohi?

Yes, but the meaning changes slightly:

Bussi ajaa pysäkin ohi. – The bus goes past the stop.
Bussi ajaa ohi. – The bus goes past (goes by) [here / us / the place in question].

Without specifying pysäkin, ohi usually refers to the current location or some contextually obvious point:

You’re standing at a stop and say:
- Bussi ajaa ohi. – The bus is going past (us/this stop). It doesn’t stop.

Is there a difference between ohi and ohitse, as in pysäkin ohi vs pysäkin ohitse?

They are very close in meaning:

pysäkin ohi – most common, neutral
pysäkin ohitse – a bit more formal/literary or slightly more emphatic, but still correct

You can generally treat ohi and ohitse as near-synonyms when used in this “past X” sense:

Auto ajoi talon ohi / ohitse. – The car drove past the house.

For everyday speech, pysäkin ohi is the usual choice.