treatise vs thesis

treatise and thesis both are nouns.

Word	Noun	Adjective	Verb	Adverb
treatise	Yes	No	No	No
thesis	Yes	No	No	No

As nouns, thesis is a hyponym of treatise; that is, thesis is a word with a more specific, narrower meaning than treatise:

treatise: a formal exposition
thesis: a treatise advancing a new point of view resulting from research; usually a requirement for an advanced academic degree

Other hyponyms of treatise include dissertation, pamphlet, tract, monograph.

treatise (noun)	thesis (noun)
a formal exposition	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