accent: a way of speaking typical of a particular group of people and especially of the natives or residents of a region dialect: a regional variety of language distinguished by features of vocabulary, grammar, and pronunciation from other

I am sorry Mandrake if I was not clear. In number 1, of course teacher has to work on his student's accent.... anyway, it was just a general question I posted in English Forum and many thanks to Mr Micawber who moved this question to TEFL