Learn Hardcore Finnish: Tarkistan, että tulostin on päällä ennen kokousta. - I check that the printer is on before the meeting.

In Finnish, a comma is typically used before a subordinate clause introduced by että (that), just like English often uses a comma (or at least a clear break) before that-clauses.
So Tarkistan, että… = main clause + subordinate clause, and the comma marks that boundary.

What exactly does että do here, and can I leave it out?

että introduces a content clause: you are checking the fact that something is true.

Tarkistan, että tulostin on päällä. = I check that the printer is on.

In standard written Finnish, you normally keep että. In casual spoken Finnish it may be omitted sometimes, but it can sound informal and may make the structure less clear.

Why is it tulostin on päällä and not some special “subjunctive” form after että?

Finnish doesn’t have an English-style subjunctive for this. After että, you usually use normal indicative forms:

on = is (present)
oli = was (past)

So että tulostin on päällä is just a normal statement embedded inside another sentence.

What does päällä mean literally, and why is it used for “switched on”?

Literally, päällä is the adessive form of pää (head/top) and means on (top of), on, upon in many contexts. Finnish also uses olla päällä as a common idiom meaning to be on / switched on / running (for devices, lights, services, etc.).

Examples:

Valo on päällä. = The light is on.
Tietokone on päällä. = The computer is on.

The opposite is pois päältä:

Tulostin on pois päältä. = The printer is off.

Is päällä the same as päälle?

No—case and meaning differ:

päällä = on (state/location), “being on” (static)
päälle = onto, “turning on / putting on” (direction/change)

Compare:

Tulostin on päällä. = The printer is on. (state)
Laitan tulostimen päälle. = I turn the printer on. (change)

Why is it ennen kokousta (partitive) and not ennen kokous or ennen kokouksen?

The preposition-like word ennen governs the partitive case. So the thing that comes after ennen is typically partitive:

ennen kokousta = before the meeting
ennen ruokaa = before food / before eating (depending on context)

You’ll see the same with ilman (without) and some other words that require partitive.

What case is kokousta, and how do I recognize it?

kokousta is the partitive singular of kokous (meeting).

A common pattern for nouns ending in -us/-ys:

kokous (nominative)
kokouksen (genitive)
kokousta (partitive)

Here it’s partitive because ennen requires it.

Why is the word order …on päällä ennen kokousta and could I move ennen kokousta earlier?

Finnish word order is fairly flexible. ennen kokousta can often be moved for emphasis or style:

Tarkistan, että tulostin on päällä ennen kokousta. (neutral: check happens before the meeting)
Ennen kokousta tarkistan, että tulostin on päällä. (sets the time frame first)
Tarkistan ennen kokousta, että tulostin on päällä. (emphasizes when you do the checking)

All are generally correct; the choice affects focus and rhythm.

Why is it Tarkistan (present tense)? Does it mean “I am checking” or “I check”?

Finnish present tense covers both:

habitual/general: I check
happening now / planned step: I’m checking / I check (before… )

Context decides. In this sentence, it commonly reads as a routine or a planned action before the meeting.

Could I use varmistan instead of tarkistan?

Often yes, with a small nuance:

tarkistan = I check / verify (often practical/technical checking)
varmistan = I make sure / ensure (more about certainty or ensuring it’s the case)

Both can fit:

Tarkistan, että tulostin on päällä… (checking the device status)
Varmistan, että tulostin on päällä… (making sure it’s on)

Why is tulostin in the nominative (basic form) and not in an object case?

Because in the subordinate clause tulostin on päällä, tulostin is the subject of the verb on (is). Subjects are typically nominative.

If you made printer the object of check, you’d use an object structure, but Finnish usually expresses this with an että-clause as shown, not by making tulostin a direct object.

How do I pronounce the key tricky parts: ä, double consonants, and että?

ä is like the vowel in cat for many speakers (but cleaner/shorter).
Double consonants (like kk in Tarkistan, tt in että) are longer: you hold the consonant briefly.
että is roughly et-tä (two clear syllables), with a longer tt than in English.