"He does not exist in reality."
Translation:Han finns inte i verkligheten.
I believe that is because Swedish requires the definite (-en) with abstract concepts like 'reality'.
I think that's going a bit too far. It's probably more correct to say that with more abstract concepts, there will be a bigger difference between how the languages treat definiteness. – I just wrote a longer answer on this page in answer to Cathal9.
A previous exercise translated "a dream or reality" as en dröm eller verklighet" and marked verkligheten as incorrect. In this exercise it must be verkligheten and verklighet is marked as incorrect. Can someone explain when reality must be translated as verkligheten and when verklighet?
Good question, not sure I can give a very good answer.
The simplest possible explanation is to say that i verkligheten is a set expression meaning 'in reality'.
For "a dream or reality" I believe it works the same in both languages – you could have said "a dream or the reality" in English, which would change the meaning of the phrase (you would be referring to some very specific reality), and that would be en dröm eller verkligheten in Swedish too. The first is the most natural expression though and making reality definite would work better if you added something else too: Is it a dream or the reality of our new situation or something like that.
For i verkligheten, there's no choice, the noun has to be definite. The reality is definite to us here according to the "you-know-which-one-I-mean" logic. There's just one reality*, so we say i verkligheten just like we say i världen 'in the world' and so on.
* in the context of this expression
The translation is given as "Han finns ej i verkligheten" but here in the comments section is shows "Han finns inte i verkligheten." I never encountered "ej" before. Are "ej" and "inte" interchangeable?
The recommended translation is Han finns inte i verkligheten. Depending on what you input, you may be shown things that are only supposed to be accepted, this is because the machinery tries to match your input to one of the accepted answers. ej is a more formal word for 'inte'. It is sometimes used on signs for shortness, like sometimes on buses it says Ej i trafik 'not in traffic'. It's a good word to understand, but you should probably never use it yourself.