Learn Essential French Prepositions

man reading book on train
"Il a lu le livre en une heure." (He read the book in an hour.). Deux / Getty Images

The prepositions en and dans both mean "in" in French, and can both express time and location. But they are not interchangeable; their usage depends on both meaning and grammar.

En expresses the length of time an action takes. Note that this means the verb is usually in the present or past.

Je peux faire le lit en 5 minutes.  I can make the bed in 5 minutes.

Il a lu le livre en une heure. He read the book in an hour.

J'ai appris à danser en un an. I learned how to dance in a year.

En is used to express the month, season,* or year in which an action takes place (calendar vocabulary):

Nous voyageons en avril.  We travel in April.

Il arrivera en hiver. He will arrive in the winter.

*Except au printemps

En can mean "in" or "to" when followed directly by a noun that doesn't need an article:

Vous allez en prison ! You're going to prison! 

Il est en classe. He's in school.

En also means "to" or "in" with some states, provinces, and countries:

J'habite en Californie I live in California

 Je vais en France I'm going to France

Dans indicates the amount of time before which an action will occur. Note that this means the verb is usually in the present or future.

Nous partons dans dix minutes.  We're leaving in 10 minutes.

 Il reviendra dans une heure. He'll be back in an hour. 

Elle va commencer dans une semaine. She's going to start in a week.

Dans refers to something that occurs within or during a decade:

Dans les années soixantes...   In the sixties... 

Dans les années quatre-vingts... During the eighties...

Dans means "in" a location when followed by an article plus noun:

Il est dans la maison. He's in the house. 

Qu'est-ce qui est dans la boîte? 

What's in the box?

Dans also means "to" or "in" with some states and provinces:

J'habite dans le Maine I live in Maine

Je vais dans l'Ontario I'm going to Ontario