Earlier quoted context omitted.
A bunch of other education-related words have different meanings on different sides of the pond. For example, UK: You write a dissertation for a masters degree and a thesis for a PhD. US: The opposite. I wonder if the terminology will converge...
In the US you never write a thesis, you write a dissertation (document) based on a thesis (idea.)
"In academia, a thesis or dissertation is a document that presents the author's research and findings and is submitted in support of candidature for a degree or professional qualification."