"He is in prison."
Translation:Hij zit in de gevangenis.
Why not "Hij is in gevangenis"? It's "prison" not "a prison" or "the prison". Is there a specific rule or is it like with "tonight" in English, thay you don't say "the tonight", but always "tonight"?
For being incarcerated zitten is always used. This usage is so clear that sentences like: Hij/zij moet zitten usually this will mean He has to do time (since there aren't that many situations where you're mentioning that a 3rd person has to sit).
If you're visiting a prison building, you could say: Ik ben in de gevangenis. You cannot leave out de in this kind of sentences, I'm not sure why, but to me it's similar to English I'm at the bank. The only similar sentences I can think of now, where you can leave out the article in Dutch are: op school and op kantoor.
I suspect it tells something about the USA (where Duo is from) rather than the Netherlands. In the French Duo-course, the vocabulary related to prison also comes fairly early in the course. I found it interesting: I learnt other foreign languages in the offline world, and "prison" was definitely not a common word to use and to practice.
This would mean that he is lying in the prison. Although it is technicaly correct, gramaticaly is not common. As i understanding it, ligt is used for things that cannot stand straight witouth something holding them like banket. Also used for location like beach, city, square.. It would be something like spreads.