Dans-côte

What about inside / outside? This is basically the same, except that '-sus' becomes '-dans' (in!) and '-sous' becomes '-hors' (out!)!

Au-dedans = inside; within
Au-dehors = outside


Remember, H is silent, so 'dehors' sounds more like a French person trying to say 'door.'

But! These are moreover for things like, say; boxes. If you want to be more clear (albeit more formal), try this:

Brian est à l'extérieur, mais son parapluie est dans la maison! = Brian is outside, but his umbrella is inside!

Pauvre Brian !