Ikkunasta tulee vetoa.

Because -sta / -stä is the elative case, which often means out of or from.

• ikkuna = window
• ikkunasta = from the window / out of the window

In this sentence, it means the draft is coming from the window area, or more naturally, through the window. Finnish often uses a from case where English would say through.

Tulee is the 3rd person singular of tulla, meaning to come.

So literally, the sentence is something like:

• From the window comes draft

That sounds odd in English, but Finnish uses tulla in expressions like this quite naturally. It can describe something appearing, entering, or being felt from a source.

So even though English might say There is a draft coming from the window or A draft is coming in through the window, Finnish can say ikkunasta tulee vetoa.

Because vetoa is the partitive singular of veto.

Here the partitive is used because draft is being treated like an uncountable phenomenon or some amount of something, rather than one clearly bounded item.

Compare the idea in English:

• There is draft coming in
• There is some draft

This is a very common pattern in Finnish with things like substances, weather, and general sensations:

• sataa vettä = it is raining water / it is raining
• huoneessa on valoa = there is light in the room
• ikkunasta tulee vetoa = there is draft coming from the window

So vetoa suggests some draft / draftiness, not one specific countable draft.

The basic form is veto.

That word has several meanings depending on context, including:

• pull
• traction
• draw
• draft

In this sentence, it means draft, as in cold moving air.

So:

• veto = draft
• vetoa = partitive form of veto

Because Finnish does not need a dummy subject the way English often does.

English often says:

• There is a draft
• It is raining

But Finnish usually does not need a meaningless subject like there or it. The verb and the rest of the sentence are enough.

So instead of something like There is draft coming from the window, Finnish simply says:

• Ikkunasta tulee vetoa

This is completely normal Finnish sentence structure.

In practice, it can suggest either, depending on how natural English would express it.

A very literal gloss is from the window, but in natural English the idea is usually:

• through the window
• from the window
• in through the window

The important idea is that the window is the source of the draft. Usually this means the window is not sealed properly, is slightly open, or lets air in somehow.

No, Finnish word order is fairly flexible, but the given order is a very natural neutral one.

This version presents the source first:

• Ikkunasta tulee vetoa

Other orders are possible, for example:

• Vetoa tulee ikkunasta
• Tulee vetoa ikkunasta

These are not random changes: they affect focus and information structure.

Very roughly:

• Ikkunasta tulee vetoa = neutral, natural
• Vetoa tulee ikkunasta = emphasizes the draft
• Tulee vetoa ikkunasta = possible in context, often more marked

So the original sentence is a good standard way to say it.

Because Finnish has no articles.

There is no separate word for a, an, or the. Whether something is definite or indefinite is understood from context.

So:

• ikkunasta could mean from the window or from a window, depending on context
• vetoa does not need an article either

In this sentence, English will usually use the window, because the speaker normally has a specific window in mind. But Finnish does not mark that with an article.

Yes. That is also a very common way to express the idea.

• Ikkunasta vetää = the window is drafty / there is a draft coming from the window

Here vetää literally means pulls, but in this kind of expression it means there is a draft.

So both are possible:

• Ikkunasta tulee vetoa
• Ikkunasta vetää

The first one uses the noun vetoa. The second one uses the verb vetää idiomatically.

Both are natural, though Ikkunasta vetää may feel a bit more everyday and direct.