Tuulen voima avasi oven.

Because tuulen is the genitive singular of tuuli (wind).

In Tuulen voima, the structure is literally the wind's force or the force of the wind. Finnish often uses the genitive case to show this kind of relationship.

• tuuli = wind
• tuulen = of the wind / wind's

So:

• Tuulen voima = the force of the wind

Voima means force, strength, or power.

In this sentence, tuulen voima means the force/power of the wind. It is the subject doing the action.

Depending on context, voima can refer to:

• physical strength
• force
• power
• energy

Here, force or power is the most natural interpretation.

Because oven is the genitive singular / accusative form of ovi (door), and here it marks the object as a complete whole that was affected by the action.

• ovi = door
• oven = the door (as a total object in this sentence)

Finnish often uses a total object when the action is completed or affects the whole object.

So:

• avasi oven = opened the door

This suggests the door was successfully opened, not just partially affected.

Because the action is understood as completed.

Compare:

• avasi oven = opened the door
  
  • completed action
  • whole object affected

If the action were ongoing, incomplete, or indefinite, Finnish might use the partitive in other kinds of sentences. But with open the door as a finished event, the total object is normal.

So oven fits because the door ended up open.

Avasi is the past tense (imperfect) of the verb avata (to open), in the 3rd person singular.

Breakdown:

• avata = to open
• hän avaa = he/she opens
• hän avasi = he/she opened

In this sentence, the subject is not a person but tuulen voima, and Finnish still uses the same 3rd person singular verb form:

• Tuulen voima avasi oven.
• The force of the wind opened the door.

The subject is Tuulen voima.

A good way to find it is to ask: What opened the door?

Answer: The force of the wind.

So the structure is:

• Tuulen voima = subject
• avasi = verb
• oven = object

Even though tuulen comes first, the full noun phrase tuulen voima works together as one subject.

Not necessarily a fixed expression, but it is a very natural Finnish noun phrase.

It is built in a common Finnish way:

• genitive noun + main noun

Examples of the same pattern:

• lapsen kirja = the child's book
• talon ovi = the house's door / the door of the house
• tuulen voima = the force of the wind

So this is a normal grammatical structure, not something unusual you just have to memorize as a whole phrase.

Grammatically yes, but the meaning would change.

• Voima avasi oven = The force/power opened the door
• Tuulen voima avasi oven = The force of the wind opened the door

Without tuulen, the sentence becomes more general and less specific. Voima alone sounds vaguer and a bit less natural unless the context already makes it clear what force is meant.

Yes, Finnish word order is fairly flexible, although the neutral order here is very natural:

• Tuulen voima avasi oven.

Other orders are possible for emphasis, for example:

• Oven avasi tuulen voima.
• Avasi oven tuulen voima.

But these are less neutral and usually sound marked, literary, or context-dependent.

For a learner, the basic order:

• subject + verb + object

is the safest and most useful here.

No. Tuulen does not mean windy.

It is the genitive form of tuuli (wind), meaning of the wind or wind's.

If you want to say windy, Finnish uses an adjective such as:

• tuulinen = windy

So:

• tuuli = wind
• tuulen = of the wind
• tuulinen = windy

Because Finnish usually expresses relationships like of, 's, and possession through case endings instead of separate words.

In English:

• the force of the wind
• the wind's force

In Finnish:

• tuulen voima

The ending -n on tuuli shows the relationship. So instead of a separate word like of, Finnish changes the noun itself.

No. Finnish does not have articles like a or the.

So Tuulen voima avasi oven can be translated into English with articles because English needs them, but Finnish does not mark them directly.

Context tells you whether something is definite or indefinite.

Here, English naturally says:

• The force of the wind opened the door.

and not usually A force of wind opened a door, unless the context is very different.

In dictionary forms, the words are:

• tuuli = wind
• voima = force, power
• avata = to open
• ovi = door

The sentence uses inflected forms:

• tuulen ← from tuuli
• voima ← dictionary form
• avasi ← from avata
• oven ← from ovi

This is very normal in Finnish: the words you see in a sentence are often not in their dictionary forms because endings show grammatical roles.