In our last lesson, we introduced the word dont, a relative pronoun with a wide variety of uses. Let's start with the two most straightforward meanings of dont: "whose" and "including":
...un riche marchand dont la fille préférée s'appelait Belle.
...there was a rich merchant whose favorite daughter was called Belle.
Caption 2, Bande-annonce - La Belle et La BêtePlay Caption
Et grâce à lui, j'ai rencontré beaucoup de gens très intéressants, dont Gilles Proulx.
And thanks to him, I met lots of very interesting people, including Gilles Proulx.
Caption 29, Le Québec parle - aux Français - Part 2Play Caption
It's usually pretty easy to distinguish these two uses of dont from context, but punctuation also provides a clue: dont is usually preceded by a comma when it means "including," but not when it means "whose."
Now let's get into the grammar behind dont. Like all relative pronouns, dont refers back to an element in the main clause (un riche marchand and gens très intéressants in the examples above). But in many cases, dont more specifically refers to the preposition de + a noun. To see how this plays out, let's look at how dont can be used to combine two sentences into one:
J'ai un chat. Le poil de mon chat est très doux.
I have a cat. My cat's fur is very soft.
J'ai un chat dont le poil est très doux.
I have a cat whose fur is very soft.
As you can see, dont stands in for de and refers back to chat. It also prevents the redundancy of saying chat twice.
Dont often replaces the de used in fixed expressions, such as être fier/fière de (to be proud of), parler de (to talk about), and avoir besoin de (to need):
Et puis il y a une chose dont Michel est particulièrement fier.
And then there is one thing that Michel is particularly proud of.
Caption 36, Le Journal - L'île de PâquesPlay Caption
...dans la ville de Dongtan en Chine, dont nous avons déjà parlé.
...in the city of Dongtan in China, about which we've already spoken.Play Caption
Voici le livre dont j'ai besoin.
Here is the book that I need.
We could rewrite all of these examples using de:
Et puis Michel est particulièrement fier d'une chose.
And then Michel is particularly proud of one thing.
Nous avons déjà parlé de la ville de Dongtan en Chine.
We've already spoken about the city of Dongtan in China.
J'ai besoin de ce livre-ci.
I need this book.
That about covers it for dont! Though the scope of its applications can be a little daunting, it's a very useful and succinct word that will make your French sound very sophisticated. Don't neglect to use dont whenever you can!