Discourse operators

Is Discourse operator the same notion as The discourse markers? i'm trying to understand the difference here...
my professor gave me a task to write a short report on discourse operators and their transposition of meanings. e.g.
"only" originally is a a particle , ,"well " - an adverb, but thruog transpositional changes they lose their primary lexical meaning and acquire processive one...
so plz, help me in this case...
i'm really confusewd.. and it's due tomorrow(the paper)... i'm still on line to check some of your replies... thanx in advance