What different criteria would you choose to classify people that you meet often?

(N/A) To classify a group of people,we can use hierarchical criteria to ensure each individual is uniquely identified.
$1$. First,we can classify based on biological sex (males and females).
$2$. Second,we can classify based on the first name of the individuals.
$3$. Third,if names are identical,we can use surnames to further distinguish them.
$4$. Finally,for absolute uniqueness,we can use a unique identifier such as an $ID$ number,roll number,or date of birth.