Tuli tuhosi vanhan talon.

Here tuli means fire.

It is the subject of the sentence: Tuli tuhosi vanhan talon = The fire destroyed the old house.

A common source of confusion is that tuli can also be a verb form meaning came (from tulla, to come). But in this sentence, it cannot mean came, because the next word tuhosi is already the main verb. So here tuli must be a noun: fire.

Tuhosi is the past tense of the verb tuhota, meaning to destroy.

More specifically, it is:

• third person singular
• past tense

So:

• minä tuhosin = I destroyed
• hän/se tuhosi = he/she/it destroyed

In this sentence, tuhosi matches the singular subject tuli.

Because vanhan talon is the object of the verb, not the subject.

In Finnish, the object often changes form. Here the action is seen as complete: the fire destroyed the whole house. Because of that, Finnish uses the total object.

With a singular noun, the total object often looks like the genitive:

• talo = house
• talon = house (object/genitive-looking form)

The adjective must agree with the noun:

• vanha talo = old house
• vanhan talon = old house (object form here)

So vanhan talon is used because the sentence refers to the house as a whole, completely destroyed.

This is a very common learner question.

In traditional grammar, the object in a sentence like this is often called the accusative object, but for singular nouns its form is usually identical to the genitive.

So in practice:

• the form talon looks like the genitive
• in function, it is the total object

Many learning materials simply say that the singular total object has the genitive form. That is a useful way to think about it at this stage.

Because in Finnish, adjectives usually agree with the noun they describe.

So if the noun changes case, the adjective changes too:

• vanha talo = old house
• vanhan talon
• vanhassa talossa = in the old house
• vanhasta talosta = from the old house

This agreement is a basic and very important Finnish pattern.

Finnish does not have articles like English a/an or the.

So:

• tuli can mean a fire or the fire
• vanha talo can mean an old house or the old house

You understand which one is meant from the context. In this sentence, English naturally uses the fire and the old house, but Finnish does not need separate article words.

Yes. Finnish word order is more flexible than English word order.

The neutral order here is:

• Tuli tuhosi vanhan talon.

But other orders are possible, depending on emphasis:

• Vanhan talon tuhosi tuli.
• Tuhosi tuli vanhan talon. (less neutral, more marked)

Even when the order changes, the case endings help show what each word is doing:

• tuli is the subject
• vanhan talon is the object

So Finnish relies less on word order and more on endings than English does.

Because the sentence describes a completed action with a total result.

Compare:

• Tuli tuhosi vanhan talon. = The fire destroyed the old house.
  → the house was completely destroyed

But the partitive object would suggest an incomplete, ongoing, or non-total action:

• Tuli tuhosi vanhaa taloa.
  This sounds unnatural in most normal contexts, because destroy usually implies a result.

A clearer comparison with another verb might be:

• Luin kirjan. = I read the book (finished it)
• Luin kirjaa. = I was reading a book / I read some of the book

So vanhan talon is used because the destruction is complete.

Yes: the verb stem changes a little in the past tense.

The basic verb is:

• tuhota = to destroy

Its past tense stem is:

• tuhosi-

So:

• minä tuhosin
• hän/se tuhosi
• he tuhosivat

This is a normal kind of Finnish verb change: the past tense is not always made by simply adding one ending to the dictionary form. Learners usually just memorize the principal forms over time.

Because talo is a very regular noun type.

Its basic forms are:

• talo = house
• talon = house's / house (total object form)
• talossa = in the house
• talosta = from the house

So here -n is the expected ending for this singular object/genitive-looking form.

This is one of the easier noun patterns in Finnish.

By itself, yes:

• Hän tuli. = He/She came.

But not here.

In Tuli tuhosi vanhan talon, if you tried to read tuli as came, then the sentence would effectively have two finite verbs:

• came destroyed...

That does not work as a normal Finnish clause. So the sentence structure tells you that tuli must be the noun fire here.