doctoral dissertation vs thesis

doctoral dissertation and thesis both are nouns.

Word	Noun	Adjective	Verb	Adverb
doctoral dissertation	Yes	No	No	No
thesis	Yes	No	No	No

As nouns, thesis is a hypernym of doctoral dissertation; that is, thesis is a word with a broader meaning than doctoral dissertation:

doctoral dissertation: A lengthy, formal treatise written by a candidate for the doctoral degree at a university.
thesis: a treatise advancing a new point of view resulting from research; usually a requirement for an advanced academic degree

Other hypernyms of doctoral dissertation include dissertation.

doctoral dissertation (noun)	thesis (noun)
A lengthy, formal treatise written by a candidate for the doctoral degree at a university.	an unproved statement put forward as a premise in an argument
	a treatise advancing a new point of view resulting from research; usually a requirement for an advanced academic degree