Hello :) Please help me

[H.Leyla]

One, who writes a dissertation - it is a dissertation writer or thesis writer or ...... ???

[JohnParis]

Usually, a candidate for a post-graduate degree will be required to write a dissertaion as the final (and most important) step in obtaining his diploma. He is the author of his own dissertation/thesis.
There are "professional" dissertation/thesis writers for hire and these people might refer to themselves as dissertation/thesis writers.
Does this answer your question? I'm not certain.
John

[H.Leyla]

Usually, a candidate for a post-graduate degree will be required to write a dissertaion as the final (and most important) step in obtaining his diploma. He is the author of his own dissertation/thesis.
There are "professional" dissertation/thesis writers for hire and these people might refer to themselves as dissertation/thesis writers.
Does this answer your question? I'm not certain.
John

Thank you for taking time to respond my question.
I have searched on the Internet and found this answer
Dissertator - One who writers a dissertation; one who discourses.
But I'm using dictionary and there is no such word at all
So I'm not sure whether I can use this word or not ?

[JohnParis]

You're welcome.
That word is not in any of my dictionaries (and I have many) and I strongly recommend that you not use it.

When you were typing your response, did you notice the red line underneath the word "dissertator"? That's the automatic spell check attached to this site. When you see that red line, you can be assured that the word is either misspelled or does not really exist.

If you found "Dissertator" (and the definition you gave) on the net, again all I can say is it is not in any of my dictionaries. When in doubt, always rely on a good dictionary - not "the net."

[riquecohen]

As JohnParis has said, either one of your original choices is correct.

May I suggest that you give more meaningful titles to your future posts? Thesis or dissertation? would have been a good title for this thread.