Ovi ei aukea, koska lukko on rikki.

Finnish usually makes negative sentences with a separate negative verb. In this sentence, that verb is ei.

So instead of doing something like English does not open, Finnish uses:

• ei = the negative verb
• aukea = the main verb in its negative form

A useful comparison:

• Ovi aukeaa. = The door opens / is opening.
• Ovi ei aukea. = The door does not open / won’t open.

The negative verb changes for person and number:

• en, et, ei, emme, ette, eivät

Here the subject is singular third person (ovi), so the correct form is ei.

Because after the negative verb ei, the main verb appears in a special form called the connegative.

For the verb aueta:

• positive 3rd person singular: aukeaa
• negative: ei aukea

So:

• Ovi aukeaa.
• Ovi ei aukea.

This is very common in Finnish:

• hän tulee → hän ei tule
• se toimii → se ei toimi

So aukea here is not a mistake; it is exactly the form the verb takes after ei.

The dictionary form is aueta.

It means to open in the sense of become open or open by itself. It is an intransitive verb, which means it does not normally take a direct object.

Examples:

• Ovi aukeaa. = The door opens.
• Ikkuna ei aukea. = The window won’t open.

So in your sentence, the focus is on what happens to the door itself, not on a person opening it.

This is a very common question.

• aueta = to open / to come open

  • intransitive
  • the thing itself is the subject

• avata = to open something

  • transitive
  • someone opens an object

Compare:

• Ovi aukeaa. = The door opens.
• Mies avaa oven. = The man opens the door.

In your sentence, ovi is the subject, so aueta is the natural choice.

They are both in the nominative singular, which is the basic dictionary form for nouns.

That is because both are the subjects of their clauses:

• Ovi ei aukea → ovi is the subject
• lukko on rikki → lukko is the subject

So:

• ovi = door / the door
• lukko = lock / the lock

Also, Finnish has no articles like a or the. The plain noun can mean either one depending on context.

So ovi can mean:

• a door
• the door

and lukko can mean:

• a lock
• the lock

The context tells you which is most natural.

Koska means because.

It introduces the reason for the first clause:

• Ovi ei aukea = the main situation
• koska lukko on rikki = the reason

So the structure is:

• main clause + koska + reason clause

You can also reverse the order:

• Koska lukko on rikki, ovi ei aukea.

That means the same thing, just with a different emphasis.

Also note the comma: in standard Finnish, a subordinate clause introduced by koska is normally separated by a comma.

Rikki means broken, out of order, or not working because it is damaged.

In sentences like this, it is often used with olla:

• on rikki = is broken

So:

• lukko on rikki = the lock is broken

For learners, the easiest way to understand it is as a very common expression meaning be broken.

It does not behave exactly like a typical adjective in all situations, so it is often best to learn olla rikki as a chunk:

• Puhelin on rikki. = The phone is broken.
• Auto on rikki. = The car is broken.

Yes, there is a small but useful difference.

• rikki emphasizes the state: broken, not functioning
• rikkinäinen is more like an ordinary adjective meaning broken or damaged

Compare:

• Lukko on rikki. = The lock is broken.
  → very natural when something does not work

• rikkinäinen lukko = a broken/damaged lock
  → more adjective-like, describing the noun directly

In your sentence, on rikki is the most natural choice because the sentence explains why the door will not open: the lock is in a broken state.

It can mean either, depending on context.

Finnish present tense often covers both:

• a present fact: doesn’t open
• a practical immediate-future meaning: won’t open

In this sentence, English speakers often translate it naturally as:

• The door won’t open, because the lock is broken.

But grammatically, Finnish is still just using the present tense.

Yes. Finnish word order is fairly flexible, although not completely free.

The sentence can also be:

• Koska lukko on rikki, ovi ei aukea.

That version puts the reason first.

The original order is very natural because it gives:

1. the problem
2. the explanation

So:

• Ovi ei aukea, koska lukko on rikki.

feels like:

• problem first, reason second

Both are correct.

Because aueta is an intransitive verb.

That means it describes something happening to the subject itself:

• Ovi aukeaa. = The door opens.

There is no direct object because nobody is opening something here.

If you want an object, you would normally use avata instead:

• Hän avaa oven. = He/She opens the door.

So in your sentence:

• ovi is the subject
• there is no object
• the door is the thing that fails to open