Origin: Latin suffix -tion
Dissertation has 2 different meanings across 1 category:
a treatise advancing a new point of view resulting from research; usually a requirement for an advanced academic degree
"After three years of rigorous study, she submitted her dissertation on quantum entanglement to fulfill the requirements for her PhD."
A formal exposition of a subject, especially a research paper that students write in order to complete the requirements for a doctoral degree; a thesis.
"After years of studying under her advisor, Maria finally defended her dissertation on quantum mechanics to earn her doctorate."
In plain English: A dissertation is a very long research paper that students write to earn an advanced degree at university.
"He spent all night writing his dissertation on local history for university credit."
Usage: Use dissertation specifically for an extended academic thesis required to earn a doctorate. Do not use it interchangeably with essay or article when referring to shorter non-academic pieces of writing.
The word comes from the Latin dissertātiō, which originally meant a detailed discussion or treatise. It is derived from the verb dissertō, meaning to discuss at length.