Mary’s dog

Is the possessive case compulsory? Do I have to say “Mary’s dog”, or can I also say “the dog of Mary”? Thanks!
Nicola

It’s not compulsory, but “Mary’s dog” is the standard form. “The dog of Mary” is not incorrect, but it sounds strange. Usually, the “Anglo-Saxon genitive” (“Mary’s dog”) is personal: it describes something that belongs to an individual person, whereas “of” is less personal: “the economy of China” (or “the Chinese economy”), rather than “China’s economy.”