Mötet är igång nu.

Because mötet is the definite form of the noun möte.

• ett möte = a meeting
• mötet = the meeting

Swedish usually adds the definite ending to the noun itself, instead of putting a separate word like the in front.

Since möte is an ett-word (a neuter noun), the definite singular ending is -t:

• ett möte
• mötet

In Swedish, the idea of the is often built into the noun as an ending.

So instead of:

• English: the meeting

you get:

• Swedish: mötet

This is one of the biggest differences from English. Swedish does sometimes use a separate definite word too, but in a simple sentence like this, mötet by itself already means the meeting.

igång means something like:

• underway
• in progress
• started and now continuing
• sometimes up and running, depending on context

In Mötet är igång nu, it means the meeting has started and is now happening.

A useful way to think of it is:

• är igång = is underway / is in progress

You will also see igång in other contexts:

• Motorn är igång. = The engine is running.
• Projektet är igång. = The project is underway.

är is the present tense of vara, which means to be.

So:

• är = is / are / am, depending on context

In this sentence:

• Mötet är igång = The meeting is underway

Swedish often uses vara + igång where English might use:

• is underway
• has started
• is in progress

It is normally written as one word: igång.

It comes historically from i gång, and you may occasionally notice variation in older texts or certain expressions, but modern standard Swedish usually writes it as igång when it means underway / running / started.

So for a learner, the safe choice is:

• igång

nu means now.

It emphasizes that the situation is true at this moment:

• Mötet är igång. = The meeting is underway.
• Mötet är igång nu. = The meeting is underway now.

So nu adds a sense of timing or immediacy.

Yes. Nu är mötet igång is also completely natural Swedish.

Both are correct:

• Mötet är igång nu.
• Nu är mötet igång.

The difference is mainly focus:

• Mötet är igång nu puts the topic the meeting first.
• Nu är mötet igång puts more emphasis on now.

This is very common in Swedish. When a time word like nu comes first, the verb usually comes next:

• Nu
  • är
    • mötet
      • igång

That is an example of normal Swedish V2 word order.

Yes, and it is similar, but not exactly identical.

• Mötet är igång nu = The meeting is underway now / has started now
• Mötet pågår nu = The meeting is currently taking place

pågår focuses more on the activity continuing.
är igång can feel a little more like has gotten started and is now happening.

In many everyday situations, they are close enough to be interchangeable.

Because Swedish main clauses usually follow the pattern:

• subject + verb + ...

Here:

• Mötet = subject
• är = verb

So:

• Mötet är igång nu.

If you move another element to the front, like Nu, then the verb comes before the subject:

• Nu är mötet igång.

That is the normal Swedish word-order rule often called verb-second.

A rough guide is:

• mötet ≈ MUR-tet or MOO-eh-tet, but neither is perfect

The hardest part for English speakers is ö, which does not exist in standard English. It is said with rounded lips.

A more useful breakdown:

• mö- has the ö sound
• -tet sounds roughly like teh-tet, with a clear t

The stress is on the first syllable:

• MÖ-tet

If you already know Swedish ö from words like söndag or för, it is the same vowel family.

A rough guide is:

• igång ≈ ee-GONG, but with a Swedish å sound, not exactly English o

Breakdown:

• i- sounds like ee
• gång has the vowel å, which is a long open rounded vowel in this word

The stress is usually on the second part:

• i-GÅNG

Also, the final ng is the normal ng sound, like in English song.

It is completely natural and neutral. You could hear it in everyday speech, at work, at school, or in announcements.

Examples:

• Mötet är igång nu, så kom in.
• Seminariet är igång nu.
• Lektionen är igång nu.

So it is neither especially formal nor especially slangy. It is just standard, useful Swedish.