"He went to a restaurant to eat dinner with his guests."

Translation: Li iris al restoracio por vespermanĝi kun siaj gastoj.

[AntoineFersing]

Why is it "siaj gastoj" and not "liaj gastoj" ? I'm affraid I can get it : it is a singular masculine, right ?

[mizinamo]

siaj means that the guests belong to the (third-person) subject.

If you had used liaj, the guests would have belonged to some other male.

[AntoineFersing]

So it is some kind of reflexive rule ? When the possessive refers to the subject, it is always sia ?

[mizinamo]

Only if the subject is third person (he, she, it, they).

So this is more like Swedish than like Russian -- we don't say Mi legas sian libron for "I read my (own) book".

[AntoineFersing]

Thank you ; it is now perfectly clear to me.

[kbalara]

Restaurant must be mangxejoj, right?

[mizinamo]

Manĝejoj would be "places to eat" (plural) - could be restaurants, dining halls, canteens, mess rooms, ....