This is the 9th most frequent Spanish word.
su
"Su" means "his," "her," "its," "your" (formal), or "their" depending on context.
In this sentence, 'su' indicates possession and refers to a singular third person.
Su libro está sobre la mesa.
Her book is on the table.
In this example, 'su' expresses possession related to a plural third person subject.
Ellos traen su comida para compartir.
They bring their food to share.
Here, 'su' is used to indicate possession and could refer to the opinion of either one individual or a group, depending on the context.