Introduction
The basic meaning of the genitive is of, denoting possession.
This possessive use can be seen in examples such as:
This is my sister's book.
which can also be expressed as
This is the book of my sister.
Keeping in the 'of' helps to avoid problems concerning the misuse of apostrophes and 's'. sister gives you the genitive sister's. sisters gives you the genitive sisters'. Names such as Sophocles or James can have genitives with an extra 's' or without one, so both Sophocles' and Sophocles's can be acceptable.
In Latin, an example would be:
fur pecuniam amici mei abstulit
The thief stole my friend's money.
The thief stole the money of my friend.
