What is the difference between scholarly, professional and opinion writing?

Question

anonymous · Answer

One is journalistic and valid but  of different and varying opinions. The other is scholarly and emanating from Journals of various Academic impacts so voice might vary.

anonymous · Answer

Scholarly journals are juried (peer reviewed), and journals allow no advertising, so there should in theory be little or no personal bias--just the presentation of research. 

Opinion pieces may be of whatever quality, but writers may editorialize according to the policies of their media outlet, whatever it is--their own blog, or the New York Times.

Not sure what type of professional writing you mean.