The possessive forms mark ownership. When the possessive is not followed by a noun, add an s at the end of the word (except in the first person):

Is that my toy or yours?

When the possessive my is not followed by a noun it becomes mine:

Your television is large, mine is small.

To indicate one human or an animal owner ‘s is used. To indicate multiple owners, the apostrophe ‘ is added after the plural s:

the teacher’s desk

somebody’s jacket

the girls’ hobbies

the animals’ food

Of-genitive is used:

• when saying that places or things belong together: the streets of London
• often with the definite article the: the sound of the fire alarm 
• for sets and pairs of things: three pairs of goggles
• for abstract things: for the sake of safety

A friend of Farshad‘s is called the double genitive in which possession is indicated both by the preposition of and the genitive ‘s. The double genitive can also be used with the preposition of + the independent form of possessive pronouns:

The man by the wooden counter is a former teacher of mine.