Thesis and dissertation are two different types of writing that are required to graduate from a PhD program. Thesis is an introductory paper, while a dissertation is a research paper that defends the work done in the thesis. 

A PhD candidate must write a thesis or dissertation and defend it in front of other members of a department or faculty. One way to accomplish this is to write an independent study report (abbreviated ISR). This document can be used as part of any master’s program or as part of your doctorate degree program.