"Nemůžu pít pivo, protože jsem dítě."

Translation: I cannot drink beer because I am a child.

[JanisaChatte]

What's the difference between můžu and mohu? Or are they interchangeable ?

[VladaFu]

Completely interchangeable, it is a different form of the same verb, but mohu is more formal, may sound bookish in spoken (except very formal) conversation.

[JanisaChatte]

Děkuji! mohu is just easier to remember... but I'll keep this in mind when\if I have a chance to use Czech in real life

[BrianG1941]

Why is 'I may not drink beer' wrong?

[VladaFu]

This is nesmím.

[VasilIslander]

But here https://forum.duolingo.com/comment/27744981 you argued that moct and smět are interchangeable (as I understood, at least in colloquial speech). So why are they not interchangeable in this case?

[Kat961424]

"I am not allowed" should be a possible solution a.f.a.i.k.

[AgnusOinas]

I was clicking on words instead of typing the sentence, and I almost created this: "I cannot drink beer because I am dead." :D Sounds like a better excuse.