This is the 364th most frequent Hungarian word.
aminek
"Aminek" means "to which" or "of which" in English, depending on context.
'aminek' is used as a relative pronoun referring to 'könyv', meaning 'whose' or 'of which'.
Ez az a könyv, aminek az íróját kedvelem.
This is the book whose author I like.
'aminek' functions as a relative pronoun referring to the thing causing joy, combining with the verb 'örül' necessitating a genitive-like structure.
Nem értem, aminek örülsz.
I don't understand what you are happy about.
Here, 'aminek' combines with 'miatt' to express causation with a relative pronoun referring to the 'reason'.