Abans que la reunió comenci, vull encendre la llum de l'oficina.

Abans que means before when it is followed by a full clause with a conjugated verb.

So:

• Abans que la reunió comenci = before the meeting starts / before the meeting begins

A useful contrast is:

• abans que
  • conjugated verb
• abans de
  • infinitive or noun

That distinction is very important in Catalan.

Because abans que usually triggers the subjunctive in Catalan when the action has not happened yet.

Here, the meeting has not started yet, so Catalan uses the present subjunctive:

• que la reunió comenci

If you used comença, that would be the indicative form, and it would sound wrong in this structure.

So this is a very common pattern:

• Abans que arribi...
• Abans que surti...
• Abans que comenci...

Because after expressions like abans que, Catalan normally uses the present subjunctive to refer to a future event.

So even though the meeting will begin in the future, Catalan says:

• abans que la reunió comenci

not:

• abans que la reunió començarà

This is similar to English in one way: English also often avoids the future in time clauses:

• before the meeting begins not usually before the meeting will begin

Catalan just goes one step further by using the subjunctive.

Not in this exact sentence.

Use abans que when what follows is a clause with its own subject and conjugated verb:

• Abans que la reunió comenci

Use abans de before an infinitive or a noun:

• Abans de començar la reunió = Before starting the meeting
• Abans de la reunió = Before the meeting

So:

• abans que la reunió comenci = correct
• abans de la reunió comenci = incorrect

Because Catalan often drops subject pronouns when they are not needed.

The verb vull already tells you the subject is I:

• vull = I want

So:

• vull encendre... = I want to turn on...

You could say jo vull encendre..., but that usually adds emphasis, contrast, or clarity.

For example:

• Jo vull encendre la llum, però ell no.
  = I want to turn on the light, but he doesn’t.

Catalan uses definite articles very naturally and often more regularly than English.

So:

• la reunió = the meeting
• la llum = the light

In this sentence, both nouns are specific:

• a particular meeting
• the light of a particular office

English sometimes uses fewer articles in similar contexts, but in Catalan they are normally required here.

Vull is the first-person singular of voler = to want.

So:

• vull = I want

Encendre means to turn on, to light, or to switch on, depending on context.

So:

• vull encendre la llum = I want to turn on the light

This is a very common structure in Catalan:

• voler + infinitive

For example:

• Vull marxar. = I want to leave.
• Vull llegir. = I want to read.

It can mean both, depending on context.

For example:

• encendre una espelma = to light a candle
• encendre la llum = to turn on the light
• encendre el televisor = to turn on the TV

So in your sentence, encendre la llum is best understood as turn on the light.

De l'oficina means of the office or more naturally in English, the office’s / in the office, depending on context.

In Catalan, possession or association is often expressed with de:

• la llum de l'oficina = the office light / the light in the office

The apostrophe appears because la becomes l' before a vowel:

• la oficina → l'oficina

So:

• de + l'oficina = of the office

Catalan often uses la llum in the singular to mean the lighting in a room or place.

So:

• encendre la llum can mean turn on the light
• in natural English, that may sometimes be translated as turn on the lights, depending on the situation

If you specifically mean several separate lights, Catalan can also use the plural:

• encendre els llums

But la llum is very common and natural for general room lighting.

Yes. Catalan word order is somewhat flexible.

Your sentence begins with the time clause:

• Abans que la reunió comenci, vull encendre la llum de l'oficina.

That is perfectly natural.

You could also say:

• Vull encendre la llum de l'oficina abans que la reunió comenci.

The meaning stays basically the same. The difference is mainly one of emphasis and flow:

• putting Abans que... first highlights the time frame
• putting Vull encendre... first highlights what you want to do

Both are correct.

The accent in reunió shows where the stress falls: the final syllable is stressed.

So it is pronounced roughly like:

• re-u-ni-Ó

This fits a common Catalan pattern with words ending in -ió.

The accent is not optional; it is part of the correct spelling.