Learn Finnish: Painava ovi avautuu. - The heavy door opens.

In English, we use the same verb for 'I open the door' and 'The door opens.' Finnish distinguishes between these. avaa comes from avata (to open something), which requires an active subject doing the action to an object. avautuu is an automative verb ending in -tua, meaning the action happens by itself or without a specific agent. Since the door is opening itself here, we must use avautua.

How exactly is avautua formed from avata?

For verb type 4 words ending in -ata like avata, the stem changes to end in -au- before adding the -tua suffix. So the stem of avata becomes avau-, giving us the new verb avautua.

Is the word painava (heavy) related to a verb?

Yes, it is formed from the verb painaa, which means 'to weigh' or 'to press'. By adding the -va suffix, it becomes a present active participle acting as an adjective. It literally means 'weighing', which we naturally translate as 'heavy'.

Why is ovi in the nominative case? Doesn't the verb 'open' usually take an object?