I've noticed that en is one of the most common troublemaker words in the French tree. Here, I'll try to give you a comprehensive guide to its uses so you never blankly stare into those headlights again.

The most important thing to realize about en is that it's both a preposition and a pronoun. These two usages should be considered completely separate, like two strangers who happen to have the same name.

<h1>En the Preposition</h1>

As a preposition, en is almost always used directly in front of a noun and without an article. It's used in the following situations:

• Locations without articles: il est en prison = he is in jail
• Time: en trois jours = in three days (learn about dans vs en)
• Doing something like or as: il agit en enfant = he's acting like a kid
• Means: voyager en train = to travel by train
• Condition or appearance: être en guerre = to be at war
• Transformation: traduire en français = to translate into French
• Material: elle est une maison en brique = she's a brick...houuuse

This preposition is also required after some verbs.

<h1>En the (Adverbial) Pronoun</h1>

If you see en without a noun wingman, you can safely bet that it's a pronoun. While there are a few ways to use it, you should notice that en is always a stand-in for something else, usually something that has already been mentioned.

En = De + Noun

In this case, en means "some (of it)" or "any (of it)" because en replaces the partitive + noun or de + noun.

• As-tu du pain ? Oui, j'en ai. = Do you have any bread? Yes, I have some.

En with Verbs that Require De

Here, en also replaces de + something, but specifically for verbs that need de to complete their meaning. For instance, let's consider the verb parler de, which means "to speak of (something)".

• Tu veux en parler? = Do you want to talk about it?

You can't just write "Tu veux parler?" because this would mean "Do you want to speak?", since parler has a different meaning without the de. If you want to use the de form while referring to something already mentioned, you replace it with en.

Note that en goes in the same place as object pronouns like lui (i.e. before the verb they qualify, except in affirmative imperatives).

En for Quantities

In a sentence where you have number + noun or an expression of quantity (e.g. with assez, beaucoup, etc.), you can replace those with en. When you do this switcheroo, you have to move the number or adverb to the end of the clause.

• Il y a beaucoup de chambres. Il y en a beaucoup.
• Je voudrais deux livres. J'en voudrais deux.

<h1>I hope this has helped!</h1>

Sources and extra readings: [1] [2] [3] [4]