Quan comença la funció, el públic fa silenci.

Here quan is a conjunction meaning when, introducing a time clause: Quan comença la funció...

Catalan quan can do two jobs:

• as a question word: Quan comença la funció? = When does the show start?
• as a conjunction: Quan comença la funció, el públic fa silenci. = When the show starts, the audience falls silent / becomes quiet.

So in this sentence, it is not asking a question. It links two parts of the sentence.

Comença is the 3rd person singular present of començar = to begin / to start.

Catalan often uses the present tense for general truths, routines, and things that regularly happen. This sentence describes a typical situation:

• Quan comença la funció, el públic fa silenci.

That is like saying:

• Whenever the performance starts, the audience becomes quiet.

So the present tense works naturally here, just as in English sentences like When class starts, everyone sits down.

La funció literally means the performance, the show, or the play/performance event, depending on context.

It often refers to a staged event such as:

• a theater performance
• a cinema showing
• a concert or other public performance

So funció is not the mathematical meaning of function here. In everyday Catalan, in this kind of sentence, it usually means a performance or showing.

El públic is a collective noun. Even though it refers to many people, Catalan treats it as grammatically singular, just like English the audience.

So you get:

• el públic fa silenci
  not
• el públic fan silenci

Because the grammatical subject is singular, the verb is singular too: fa.

Yes, fer silenci is a common Catalan expression.

Literally, fa silenci means makes silence, but in natural English it means:

• becomes quiet
• falls silent
• keeps quiet
• is silent

So this is an idiomatic use of fer. Catalan uses fer in many expressions where English uses a different verb.

Some related examples:

• Feu silenci! = Be quiet!
• Els alumnes fan silenci. = The students are quiet / fall silent.

Fa is singular because its subject is el públic, which is grammatically singular.

Here is the structure:

• el públic = the subject
• fa = 3rd person singular of fer
• silenci = the noun object/complement in the expression fer silenci

So even though the audience contains many people, Catalan grammar still treats públic as singular.

The comma separates the introductory time clause from the main clause:

• Quan comença la funció, = subordinate clause
• el públic fa silenci. = main clause

This is very similar to English punctuation:

• When the performance starts, the audience falls silent.

In shorter sentences, comma use can vary a little in informal writing, but here the comma is completely normal and standard.

Yes. Catalan can also place the main clause first:

• El públic fa silenci quan comença la funció.

This means the same thing.

The version with Quan first gives a slightly more natural when X happens, Y happens structure and emphasizes the time relationship right away.

The ç is called ce trencada in Catalan. It represents an s sound, not a k sound.

So comença is pronounced roughly like ko-MEN-sa, not ko-MEN-ka.

Why use ç? Because before a, o, and u, plain c would normally sound like k. The ç tells you it must sound like s.

Compare:

• casa → k sound
• comença → s sound because of ç

The ending -a here marks the 3rd person singular present form of començar.

So:

• jo començo = I start
• tu comences = you start
• ell/ella comença = he/she starts
• la funció comença = the performance starts

Because the subject is la funció (singular), Catalan uses comença.

There are alternatives, but fer silenci is very common and natural.

Possible alternatives include:

• el públic guarda silenci = the audience keeps silent
• el públic calla = the audience is quiet / stops talking
• el públic queda en silenci = the audience falls into silence

Still, fa silenci is simple, common, and a very useful expression to learn.