This is the 410th most frequent Afrikaans word.
waarop
"Waarop" means "on which" or "upon which" in English.
In this sentence, 'waarop' refers to the object of waiting and is part of a relative clause.
Dit is die boek waarop ek gewag het.
This is the book I was waiting for.
Here, 'waarop' functions as a question word asking about the basis of the argument.
Waarop baseer jy jou argument?
On what do you base your argument?
In this case, 'waarop' links the concept to its role in forming the basis for the discussion.