Learn Hardcore Finnish: Palaverihuone on varattu tänään.

Context tells you whether palaverihuone means a meeting room or the meeting room. In a typical office context, Palaverihuone on varattu tänään will be understood as:

The meeting room is reserved today.

If you really need to specify which meeting room, you usually add more information:

Tämä palaverihuone on varattu tänään. – This meeting room is reserved today.
Iso palaverihuone on varattu tänään. – The big meeting room is reserved today.

What exactly is on doing here? Is on varattu one unit like in English is booked?

On is the 3rd person singular form of olla (to be): hän on / se on = he/she/it is.

In Palaverihuone on varattu tänään:

palaverihuone = subject
on = is
varattu = reserved (past passive participle of varata, to reserve/book)

So on varattu works together, very much like English is reserved / is booked, but grammatically it is:

copula verb (on) + participle used as an adjective (varattu)

Is varattu here a verb form or an adjective?

Morphologically, varattu is the past passive participle of varata (to reserve).

Functionally in this sentence, it behaves like an adjective describing a state:

Palaverihuone on varattu.
The meeting room is (in a state of being) reserved.

Compare with a more obviously adjectival word:

Palaverihuone on uusi. – The meeting room is new.
Palaverihuone on varattu. – The meeting room is reserved.

So you can think of varattu here as an adjective meaning reserved / booked, formed from the verb varata.

Is on varattu closer to is reserved or has been reserved in English?

It can correspond to both, depending on context, because Finnish does not separate is reserved vs has been reserved in the same way.

Palaverihuone on varattu tänään.
- The meeting room is reserved today.
- Or: The meeting room has been reserved for today.

The focus is on the current state: the room is not free today. Whether you translate it with English present simple passive (is reserved) or present perfect passive (has been reserved) depends on what sounds more natural in context.

If you want to emphasize the action of booking rather than the state, you’d use a different structure, e.g.:

Palaverihuone varattiin eilen. – The meeting room was booked yesterday. (event, not state)

Could I also say Palaverihuone on tänään varattu? Is that different?

Yes, Palaverihuone on tänään varattu is also correct.

Word order in Finnish is quite flexible and is often used for emphasis:

Palaverihuone on varattu tänään.
→ Slightly more neutral; time (tänään) comes at the end.
Palaverihuone on tänään varattu.
→ Slight emphasis on today; something like “Today, the meeting room is (the one that) is reserved.”

In everyday speech, both are fine and often interchangeable. For a beginner, you can treat them as meaning the same thing.

Where can tänään appear in the sentence? Does it always go at the end?

Common positions for tänään in this sentence type:

Tänään palaverihuone on varattu.
Palaverihuone on tänään varattu.
Palaverihuone on varattu tänään.

All are grammatically correct. Subtle differences:

Starting with Tänään puts strong emphasis on today as the topic: As for today, the meeting room is reserved.
Placing tänään before varattu or at the end is more neutral; prosody (spoken stress) then carries most of the emphasis.

For basic use, remember: adverbs of time like tänään, huomenna, nyt, pian can usually go very flexibly, especially at the beginning or end of the sentence.

How do I say The meeting room was reserved yesterday instead of is reserved today?

You mainly need to change the tense of olla and the time adverb:

Palaverihuone oli varattu eilen.
= The meeting room was reserved yesterday.
(It was in a reserved state at that time.)

Structure:

palaverihuone – subject
oli – past of on (was)
varattu – reserved
eilen – yesterday

If you want to emphasize the booking event rather than the state, you can use the passive past of varata:

Palaverihuone varattiin eilen. – The meeting room was booked yesterday. (somebody booked it yesterday)

What is the opposite of varattu in this context? How do I say The meeting room is free today?

The natural opposite is vapaa (free, available).

Typical ways to say it:

Palaverihuone on vapaa tänään.
– The meeting room is free today.

You may also hear:

Palaverihuone on vapaana tänään.
Here vapaana is an essive form, often used for temporary states. In practice, on vapaa and on vapaana are both common; on vapaa is simpler for learners.

How do I make Palaverihuone on varattu tänään negative?

Use the negative verb ei and the base form ole of olla:

Palaverihuone ei ole varattu tänään.
– The meeting room is not reserved today.

Pattern:

Affirmative: X on Y. – X is Y.
Negative: X ei ole Y. – X is not Y.

So:

Palaverihuone on varattu tänään.
Palaverihuone ei ole varattu tänään.

Is there any difference between varattu and varattuna in sentences like this?

Yes, there is a nuance:

varattu – nominative form, used as a plain adjective: reserved
- Palaverihuone on varattu tänään.
  → Focuses simply on the fact that it is booked.
varattuna – essive form, often emphasizing a temporary or current state / manner: being reserved, in a reserved state
- Palaverihuone on tänään varattuna.
  → Grammatically fine; can sound a bit more descriptive, like it is in a reserved state today.

In everyday speech about rooms, on varattu is the default. Use varattu as your standard form here; varattuna is more advanced and often not needed.