Breakdown of Nikt nie rozwiązał tej zagadki, dlatego to tajemnica.
to
this
nie
no / not
ten
this (m)
tajemnica
mystery
Questions & Answers about Nikt nie rozwiązał tej zagadki, dlatego to tajemnica.
Why does this sentence use dlatego instead of dlatego że?
Dlatego means "that is why" or "therefore" and introduces the result of an action. Here, the result is that it remains a mystery. If you wanted to say "because" to introduce the reason, you would use dlatego że and flip the sentence: To tajemnica, dlatego że nikt nie rozwiązał tej zagadki (It is a mystery because nobody solved this puzzle).
I see nikt and nie together. Do they cancel each other out?
No, Polish uses double negation. When you use a negative word like nikt (nobody), you must also put nie (not) before the verb. So while English says "Nobody solved it," Polish literally says "Nobody did not solve it."
What case is tej zagadki and why?
It is in the Genitive case. Normally, the direct object of solving something takes the Accusative case. However, because the verb is negated by nie, the object automatically switches to the Genitive case.
Why does rozwiązał have a masculine past tense ending if "nobody" does not have a gender?