A manual for writers of research papers, theses, and dissertations, Ninth edition - Kate L. Turabian 2018

Turn your working hypothesis into a claim
Constructing your argument
Research and writing

We described the early stages of research as finding a question and imagining a tentative answer. We called that answer your working hypothesis. Now as we discuss building an argument to support that hypothesis, we change our terminology one last time. When you think you can back up your hypothesis with good reasons and evidence, you’ll present that hypothesis as your argument’s claim. A claim is an assertion (which could be one sentence or several) that demands support. Your main claim is the assertion supported by your whole research argument. Some call this assertion your thesis.