What is a thesis?
A final research project, usually a paper, produced to earn a degree. In the US theses (the plural form) are typically a requirement for a master’s degree; sometimes a student can choose to write a thesis or complete a comprehensive examination.
Occasionally the independent research requirement in a doctoral degree will be called a thesis, although dissertation is more common.
Some undergraduate degrees require (or offer as an option) a thesis. Usually the student “defends” the thesis before a faculty panel.