Difference between "Thesis" and "Dissertation"

A Thesis is a scholarly written document of a smaller study on a particular topic in consistent with every details of Research Methodology. It's written usually for obtaining a Masters Degree.

A Dissertation is a scholarly document of a larger study on a particular topic in consistent with every details of research Methodology. It's wriiten usually to obtain a Doctoral Degree.

A thesis is for an M.S.

A dissertation is written for a PhD.

American English speakers are being a bit pedantic and stubborn in this thread. The words are used fairly interchangeably if you are not a bookish American (and if you are only considering the sense of "long essay for a university", which is the only sense the word dissertation has).

 I think every study has its originality at their setting.

I can assure you, as a person who has written a thesis and is currently in the process of completing a dissertation (for a Ph.D.), that the two are not completely the same.  With the thesis, there was much less work and stress.  In general, a thesis is a farely long piece of written work that demonstrates an individual's competency as part of the completion of a Master's Degree while the dissertation is a similarly long (often longer and more detailed) piece of written work that demonstrates competency at research and writing as part of the completion of a doctorate (i.e. Ph.D.) degree.  Another part of it's purpose is to contribute to the existing literature and research..but trust me when I say that I would not wish a dissertation on my worst enemy! ugh!!!