Translating "in" and "on"

Question

I've been told that you should use "dans" when there is a roof, and "sur" when there isn't. So "on the bus/plane" is "dans l'autobus/avion" and "in the fields" is "sur les champs". Is this a good general rule?

Céline Pickard · Accepted Answer

Bonjour H,
I would say that it's a helpful starting point but it oversimplifies how French prepositions work. Take a look below:
Le papier est dans le tiroir. = The paper is in the drawers.
Les clés sont dans le sac. = The keys are in the bag.
-> "tiroir" and "sac" do not "have" a roof and yet, you can use "dans".
Also, you will not tend to say "sur les champs" to mean "in the fields" but rather "dans les champs".
Take a look here for more details on French prepositions: French Prepositions
I hope this is helpful.
Bonne journée !