What determine someone's contribution to a research paper as an author ?

Usually the first author makes that decision. The first author might be the person who thought up the idea, they might be the one who did the research, they might be the one who wrote the paper, they might be the one who funded the research, they might be the head of the lab, they might have the first last name alphabetically, or any combination of that. It depends on the field; every field has their own conventions for who gets on the paper and in what order they appear. In general, if you made a substantial contribution to the paper, you will be a co-author. I've put people on my papers for pretty much no contribution, and I've been left off papers I thought I should have been second author on. There's no general rule, and it's hard to find someone to complain to.

a sort of factors ensue. often, the 1st author is meant to be the only whose contribution is maximum mandatory, and so on. often times, the place there's a great undertaking, the place the contributions of many authors are comparable, some or all of the authors' names would be in alphabetical order. interior the organic and organic technology, often the final author is the pinnacle of the study team, extremely than unavoidably the guy who contributed the least.