Learn Hardcore Finnish: Jos ovi on auki, suljen sen heti. - If the door is open, I close it immediately.

Finnish doesn’t use articles (a/an/the) at all. Whether ovi means a door or the door is understood from context. In this sentence, the situation clearly points to a specific door, so English uses the, but Finnish just uses ovi.

What does jos do in Jos ovi on auki, ...?

Jos means if and introduces a conditional subordinate clause. The structure is:

Jos + clause, then the main clause. So Jos ovi on auki = If the door is open.

Why is there a comma in Jos ovi on auki, suljen sen heti?

In Finnish, it’s standard to use a comma between a subordinate clause and the main clause when the subordinate clause comes first:

Jos ... , ... If you reverse the order, you still usually use a comma:
Suljen sen heti, jos ovi on auki.

Why does Finnish say ovi on auki (literally “door is open”) instead of just ovi auki?

The neutral, complete sentence uses the verb olla (on = is) to link the subject to its state:

ovi on auki = the door is open You may see Ovi auki! in signs/instructions or casual speech, but the full form with on is the standard general statement.

What exactly is auki here—an adjective, a noun, or something else?

Auki behaves like a predicative word meaning open (often treated as an adverb-like predicate complement in Finnish descriptions). It commonly appears in expressions like:

on auki = is open
on kiinni = is closed It doesn’t inflect like a typical adjective in this use; it’s more of a fixed state expression.

Why is suljen in the present tense if the English meaning can be “I’ll close it”?

Finnish often uses the present tense to express future actions when the future meaning is clear from context (like an if-clause or a time word). So suljen can naturally mean I close / I will close depending on context.

What does suljen tell me grammatically?

Suljen is the 1st person singular present form of sulkea (to close):

(minä) suljen = I close / I will close The -n ending signals I, so the subject pronoun minä is usually unnecessary.

Why is sen used for “it,” and what case is it?

Sen is the object form of se (it/that). Here it functions as a definite total object (you close the door completely), so Finnish uses the accusative-type form that looks like genitive:

suljen sen = I close it (completely)

Could I drop sen and just say Jos ovi on auki, suljen heti?

You can omit the object if it’s obvious, but it’s less explicit. Suljen sen heti clearly means you close it (the door). Suljen heti sounds more like “I’ll close (something) right away,” with the object left implicit.

Can I change the word order, like Suljen sen heti, jos ovi on auki? Does it change the meaning?

Yes, that word order is normal. The meaning stays the same, but the emphasis changes:

Jos ovi on auki, suljen sen heti. emphasizes the condition first.
Suljen sen heti, jos ovi on auki. emphasizes the action first.

What about adding niin: Jos ovi on auki, niin suljen sen heti?

Niin can be used like “then” to highlight the consequence (“if X, then Y”). It’s common in speech and fine in writing, but it’s optional:

Jos ..., (niin) ...