Heyall, just asking a question out of curiousity.
I'm a mathematics undergraduate, who likes to write quite detailed notes from textbooks as a method of revising. These notes tend to follow roughly the structure of the textbook chapters - with the same definitions, theorems, etc - but often with differing proofs and exposition. I've been told by classmates that these notes are quite useful for them for revision.
Now, I have no intention of ever turning these notes into anything other than notes - I wasn't even sure about keeping them after the exams ended - but thinking about doing so raised questions for me.
When writing a textbook, what precisely constitutes plagiarism?
For example, in an Abstract Algebra textbook, there are only so many ways to cover group theory - as far as I can tell, the only major differences between how several books I've seen cover group theory is in the exposition and superficially in the proofs and definitions.
If a mathematician was annoyed that the only textbook in his/her subfield was notoriously low on detail, and wrote a book that was very similar - with the exception that it were an easier read - would that constitute plagiarism? (If so, that seems a bit restrictive to me.)
It cannot be that textbooks only contain original research, else few textbooks on undergraduate maths could've been written in the last one hundred years.
When writing something which is aimed at becoming public, free or not, the rule is extremely simple: everything you have not created/discovered/written all by yourself has to be accompanied by a reference to the original work.
If you copied & pasted full sentences to your notes (which you could do at that time because your notes were private), you will have to either attribute them to their author(s) or rewrite them with your own words.
It is clear that the most difficult part will be to identify the sentences you have copied & pasted. IMHO, it would be easier to completely rewrite your notes while keeping the overall structure.