'Dissertation' and 'Thesis' – Two facets of academic research
Majority of universities the world over do indeed differentiate between thesis and dissertation, as belonging to two levels of educational research, whereas some universities treat the terms as interchangeable. While the differences may be obvious, they can also be interpreted as wafer thin. Hence, there is confusion between the descriptions thesis and dissertation as prevailing in the minds of most academics.
A thesis emphasizes research to a higher degree of academic achievement whereas dissertation denotes detailed references combined with observations made by the author, often at the graduation level. Both are research oriented activities, with thesis leading to the attainment of a doctorate or PhD degree while a dissertation culminates in a post graduate degree like MPhil. The reverse could apply in American universities, thereby adding to the confusion, with a dissertation leading to a PhD and a thesis produced while enrolled in a Master's program.
A thesis has to be on an original subject, based on a hypothesis that is submitted as a 'synopsis', allotted by a university and written under the overall supervision of a university-designated guide. For a dissertation one has to synthesize information collected, adding original thoughts to it. A thesis is considered a brief document whereas a dissertation has to be long in support of the knowledge one has acquired through research on any given subject.
To put it differently, in a thesis one has to substantiate the hypothesis with original research work. The hypothesis or the 'synopsis' should contain the gist of the new findings one has made on a subject of research. The written thesis should contain all details of original research work that one has made on the subject. (A thesis may be subjected to scrutiny for any plagiarism to determine the originality of the effort.)
In contrast, it is adequate if one has a decent knowledge of the new discoveries in order to arrive at the conclusion effectively conveyed through a dissertation. Another finite difference between the two is that in a thesis analysis of any existing literature is added, whereas a dissertation by itself is an analysis of any existing literature. More on dissertation transcription.