I c
an �t read your contribution ueslteacher??? All little black squares.
Here �s how I use the words:
The words are quite similar. It is just a matter of usage.
For me: Sure is informal (US English) but heard everywhere now. Certainly is more formal.
Informal use:
Can I come too? Sure
Can I come too? Of course you can. (Of course sounds a bit abrupt without You can etc. )
Are you going? Of course. (Abrupt on purpose:Why would you think I �m not going?)
More formal:
May I pay by credit card? Certainly Sir.
May I pay by credit card? Of course Sir. We have credit card facilities at the main desk.