It is used as a kind of possessive case.

The marking of possessive case (as in the cat's whiskers).

The accusative case and possessive case are marked with suffixes.

Thus we have the possessive case expressing this relationship by the 's.

It corresponds to the possessive case in English.

Theirs was a creativity forever in the possessive case: wife of, mother of, daughter of.

The possessive case is used to show possession, such as "Where is your coat?"

A genitive or possessive case is available as an alternative to the preposition de.

To show the possessive case (as in the cat's whiskers).