"Do you like athletics?"
Translation:Dych chi'n hoffi athletau?
Should there be a definite article before "athletau"? Or is athletau an exception to the rule?
There is no need for the definite article in this sentence.
The question is asking about 'athletics' in general.
If the question was 'Do you like the athletics'? referring perhaps to some athletics on TV then the definite article would be needed.