Dear Sirs:

Through all studying years,a question crossed my mind and still it is there.This question is:" why do we have "discourse analysis" and " conversation anaylsis"?! "" . I have tried alot to know why but in vain ; becouse I never can I find why orginaly lingists separate "discourse" apart from "conversation"!! I find no differences.. so please can one here show me what is the sory of those four terms: "discourse","conversation","discourse analysis", "conversational analysis"? I will be so grateful.

Note: I need an explanation not web sites becouse I have tried lots of sites.

Thanks a lot