| #2 (permalink) Sat Aug 12, 2006 19:49 pm Good at
I think it's impossible to limit and define the use of a particular preposition. All I can say is that on has the sense of on the topic of/on the subject of as in: There is a film tonight on tv on the war. At generally is less direct so we say: good at/clever at/bad at/.
I have done a piece on prepositions and their use for this site, which you may find useful
ESL Lesson: Prepositions
English as a Second Language
You can read my ESL story Present Simple
Joined: 27 Sep 2003