Questions & Answers about Hvad der fascinerer mig, er min egen hjerne.
Why do we need der in Hvad der fascinerer mig instead of just using Hvad?
When "what" acts as the subject of a relative clause in Danish, you must use hvad der. If you only used hvad, it would look like a direct question ("What fascinates me?"). Adding der makes it a relative clause meaning "that which fascinates me."
Is the comma before er mandatory, even though it separates the subject from the verb?
Yes, if you are using standard Danish grammatical commas. Danish requires a comma between clauses. Because Hvad der fascinerer mig is a full subordinate clause acting as the subject of the main sentence, the comma marks the boundary before the main clause verb er.
Why isn't there inversion after the comma? Doesn't a starting clause usually force the verb to come first?
The verb er actually is in the V2 (verb-second) position here! The entire free relative clause Hvad der fascinerer mig counts as the single subject taking up the first position. Therefore, the main verb er naturally follows it in the second position, with no special inversion needed.
Why do we use egen here instead of eget?
The word for "own" acts like an adjective and must agree with the noun it belongs to. Because hjerne (brain) is a singular, common-gender (en) noun, we use egen. If the noun were neuter (like et hus), you would use eget, and for plurals, you would use egne.