As a preposition:
* de: This is the most common translation. It's used for possession, origin, material, and other relationships.
* Example: "The book of John" becomes "Le livre de Jean."
* Example: "A cup of coffee" becomes "Une tasse de café."
* à: This is used for location or destination.
* Example: "The city of Paris" becomes "La ville de Paris."
* Example: "He went to the city of London" becomes "Il est allé à la ville de Londres."
* sur: This is used for things that are on top of something else.
* Example: "The cover of the book" becomes "La couverture du livre."
As a part of a phrase:
* des: The plural form of "de".
* Example: "Some of the books" becomes "Quelques-uns des livres."
* du: The masculine singular form of "de".
* Example: "A piece of the cake" becomes "Un morceau du gâteau."
* de la: The feminine singular form of "de".
* Example: "A slice of the pizza" becomes "Une part de la pizza."
It is important to consider the context and the type of noun being used to determine the correct translation of "of".
For example, if you are talking about a physical object, "de" is usually the correct translation. If you are talking about a place, "à" is usually the correct translation.
It is always best to check a dictionary or grammar guide if you are unsure of the correct translation.