Ilmanvaihto toimii automaattisesti.

Ilmanvaihto is a compound noun:

• ilma = air
• vaihto = exchange, change

So literally it is something like air exchange. In normal usage, it means ventilation.

Compound nouns are extremely common in Finnish, so this is a useful pattern to notice.

It is in the nominative singular, which is the basic dictionary form.

In this sentence, ilmanvaihto is the subject of the sentence, so the basic form is what you would expect:

• Ilmanvaihto toimii automaattisesti.
• Ventilation functions automatically.

The verb is toimia, which means:

• to function
• to work
• to operate

So toimii means functions / works / operates.

This is different from on, which is the verb olla = to be.

So compare:

• Ilmanvaihto toimii automaattisesti. = The ventilation works/operates automatically.
• Ilmanvaihto on automaattinen. = The ventilation is automatic.

Both are possible, but they say slightly different things. The original sentence focuses on how it operates, not just on a general property.

Because this is the 3rd person singular present tense form of toimia.

The basic verb is:

• toimia = to function, to work

Its present tense forms include:

• minä toimin = I function / I work
• sinä toimit = you function / you work
• hän toimii = he/she/it functions
• se toimii = it works

So in the sentence, ilmanvaihto is singular, and the verb matches that:

• Ilmanvaihto toimii. = Ventilation works/functions.

Because Finnish does not need a separate pronoun here.

In English, you might say:

• It works automatically.

But in Finnish, if the subject noun is already stated, that is enough:

• Ilmanvaihto toimii automaattisesti.

So Finnish does not add an extra it after the noun.

Automaattisesti is an adverb, meaning automatically.

In Finnish, many adverbs are formed from adjectives with -sti:

• automaattinen = automatic
• automaattisesti = automatically

This is somewhat similar to English -ly:

• automatic → automatically

So here:

• toimii automaattisesti = works automatically

Yes, but it means something a little different.

• Ilmanvaihto toimii automaattisesti.
  = The ventilation operates automatically.

• Ilmanvaihto on automaattinen.
  = The ventilation is automatic.

The first sentence describes the way it functions.
The second describes a quality or characteristic of the system.

In many situations, both are natural, but they are not exactly interchangeable.

This is a very normal, neutral Finnish word order:

• subject: ilmanvaihto
• verb: toimii
• adverb: automaattisesti

So it follows a straightforward pattern:

• [Subject] [Verb] [How]

Finnish word order is fairly flexible, but this version sounds neutral and natural.

Yes. Finnish allows word order changes more easily than English, but the emphasis changes.

For example:

• Ilmanvaihto toimii automaattisesti.
  Neutral: the ventilation operates automatically.

• Automaattisesti ilmanvaihto toimii.
  Marked/emphatic: automatically, the ventilation operates.

• Toimii ilmanvaihto automaattisesti?
  This would sound unusual by itself and would usually need a special context.

So the original order is the safest and most natural for a learner.

Not exactly.

• ilmanvaihto = ventilation
• ilmastointi = air conditioning

This is an important distinction. Ilmanvaihto is about air circulation/exchange, not necessarily cooling the air.

So if you are talking about a building system that replaces indoor air with fresh air, ilmanvaihto is the right word.

Because Finnish has no articles.

English uses:

• a
• an
• the

Finnish does not. So ilmanvaihto can mean:

• ventilation
• the ventilation

The exact meaning depends on context.

A simple pronunciation guide:

• Ilmanvaihto ≈ EEL-man-vai-h-to
• toimii ≈ TOY-mee
• automaattisesti ≈ AU-to-maat-ti-ses-ti

A few helpful points:

• Stress in Finnish is usually on the first syllable:

  • ILmanvaihto
  • TOImii
  • AUtomaattisesti
• ai in vaih sounds like the vowel sound in English eye.
• oi in toi sounds roughly like oy in boy.
• Double vowels are pronounced longer:
  • toimii
  • automaattisesti has aa

Finnish pronunciation is quite consistent, so once you know the sound rules, reading gets much easier.

You would say:

• Ilmanvaihto ei toimi automaattisesti.

This means:

• The ventilation does not work automatically.

Here:

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

So compare:

• toimii = works
• ei toimi = does not work

A few useful things:

1. Compound nouns

   • ilmanvaihto = ilma + vaihto

2. Common everyday verb

   • toimia is very useful for machines, systems, plans, and methods:
     • Se toimii. = It works.
     • Järjestelmä toimii hyvin. = The system works well.

3. Adverbs in -sti

   • automaattisesti = automatically

4. No articles

   • Finnish does not use a/an/the

5. Neutral word order

   • Subject + verb + adverb is a good default pattern

This sentence is actually a very good example of basic Finnish sentence structure.