質問: On the surface, many Japanese-English dictionaries define both する and やる as "to do", with little extra context. Offhand, I know the following: * やる and する are not interchangeable when it comes to する verbs (e.g. `× 死亡やる`) * やる also has a number of additional senses along the lines of "to give", especially where the recipient is an inferior Setting aside the second point for now, what's the 使い分け for the two words in the context of "to do"?
回答: It is difficult to distinguish the usage of them clearly. But I think, generally, やる is informal, する is not informal (but not formal). Of course it depends on the context, verb, etc.