This is the 152nd most frequent Czech word.
svůj
"Svůj" means "one's own."
The possessive pronoun "svůj" is used to refer to something owned by the subject of the sentence, in this case, "ký".
Každý si musí chránit svůj majetek.
Everyone must protect their own property.
Here, "svůj" indicates possession related to the subject "Petra," emphasizing that the favorite mug belongs to her.
Petra má svůj oblíbený hrnek.
Petra has her favorite mug.
"Svůj" here replaces "tvůj" and indicates possession of the passport by the subject "you," matching the reflexive meaning.