Meidän automme on iso.

Finnish often shows possession in two ways at once:

• meidän = our
• -mme attached to the noun = our

So:

• meidän auto = our car
• automme = our car
• meidän automme = also our car

In careful standard Finnish, meidän automme is fully correct. To an English speaker it can feel like double possession, but in Finnish this is normal in formal or standard style.

In everyday spoken Finnish, people very often say just:

• meidän auto

instead of meidän automme.

Meidän is the genitive form of me (we).

So:

• me = we
• meidän = our / of us

This is the form used before a noun to show possession:

• meidän talo = our house
• meidän automme = our car

So even though it translates as our, grammatically it is the genitive form of we.

Automme is made from:

• auto = car
• -mme = our

So:

• auto
• auto + mme
• automme = our car

Nothing else is happening here besides adding the possessive suffix. The final o stays, and the suffix attaches directly.

Also notice the double mm. In pronunciation, that consonant is held a little longer than a single m.

No.

You may see:

• automme = our car
• meidän automme = our car
• meidän auto = our car

But they are not all equally common in all situations.

A useful rough guide:

• automme: more written, formal, or literary
• meidän automme: standard and explicit
• meidän auto: very common in speech

So you do not always need both. Finnish allows different styles here.

Because automme is the subject of the sentence.

The sentence structure is:

• Meidän automme = subject
• on = is
• iso = big

Since the subject is in the basic form, the noun appears in the nominative form, with the possessive suffix added:

• auto → automme

It is not in the genitive, partitive, or another object-related case, because this is not an object here.

Because iso is a predicate adjective after the verb on (is).

In English:

• Our car is big.

In Finnish:

• Meidän automme on iso.

This is the normal pattern:

• subject + on
  • adjective

Compare:

• iso auto = a big car / the big car
  Here iso comes before the noun and describes it directly.

• auto on iso = the car is big
  Here iso comes after on and is the predicate.

So iso is at the end because the sentence means the car is big, not the big car.

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

The neutral, basic order is:

• Meidän automme on iso.

But other orders are possible for emphasis, contrast, or style, for example:

• Iso on meidän automme.
• Meidän automme iso on is generally not natural in normal usage.

Even though Finnish is flexible, learners should first use the standard neutral order:

• subject + verb + complement

So this sentence is the safest and most natural basic version.

Yes, but that means The car is big or A car is big, depending on context, not Our car is big.

You would be leaving out the possession.

Compare:

• Auto on iso. = The car is big.
• Meidän auto on iso. = Our car is big.
• Meidän automme on iso. = Our car is big.

So meidän / -mme is what gives the meaning our.

On is the third-person singular form of the verb olla (to be).

So:

• olen = I am
• olet = you are
• on = he/she/it is

Since automme (our car) is singular, Finnish uses on:

• Meidän automme on iso.

If the subject were plural, the verb would change:

• Meidän automme ovat isoja. = Our cars are big.

Because Finnish has no articles.

English needs words like:

• a car
• the car

Finnish does not have separate words for these. Context tells you what is meant.

So:

• auto can mean a car or the car
• meidän auto / automme means our car

That is why the Finnish sentence has no word corresponding to the.

A careful approximate pronunciation is:

• Meidän ≈ MAY-dahn
• automme ≈ AU-tohm-meh
• on ≈ on
• iso ≈ EE-so

A few useful notes:

• ei in meidän is a diphthong.
• au in auto is also a diphthong.
• mm in automme is long, so hold the m slightly.
• Stress in Finnish usually falls on the first syllable:
  • MEI-dän
  • AU-tom-me
  • I-so

Meidän automme on iso. sounds correct and natural in standard Finnish, especially in writing or careful speech.

In everyday spoken Finnish, many speakers would more likely say:

• Meidän auto on iso.

And in very casual speech, pronunciation may change too, for example:

• Meiän auto on iso.

So the sentence you have is a good model for standard Finnish, but spoken Finnish often simplifies possessive forms.