Quan tots els convidats siguin aquí, felicitarem l'oncle i li donarem el regal.

to be

Breakdown of Quan tots els convidats siguin aquí, felicitarem l'oncle i li donarem el regal.

• aquí: here
• i: and
• li: him

Questions & Answers about Quan tots els convidats siguin aquí, felicitarem l'oncle i li donarem el regal.

Why is siguin used after quan instead of an indicative form like són or seran?

Because Catalan normally uses the present subjunctive after quan when the clause refers to a future situation.

So:

• Quan tots els convidats siguin aquí... = when all the guests are here / have arrived
• not quan tots els convidats seran aquí in standard Catalan

This is a very common pattern:

• Quan arribi, parlarem. = When he arrives, we’ll talk.
• Quan ho sàpiguen, t’avisaran. = When they find out, they’ll let you know.

If quan refers to something habitual or already factual, Catalan uses the indicative instead:

• Quan tots els convidats són aquí, comencem. = When all the guests are here, we start.

So in your sentence, siguin appears because the guests are not here yet at the moment of speaking.

What exactly is siguin?

Siguin is the 3rd person plural present subjunctive of ser.

Here is the present subjunctive of ser:

• jo sigui
• tu siguis
• ell/ella sigui
• nosaltres siguem
• vosaltres sigueu
• ells/elles siguin

It matches tots els convidats, which is plural, so siguin is the correct form.

Why does the sentence use ser in siguin aquí? Why not estar?