When we say dissertation/thesis format we can also mean dissertation/thesis style. These two word combinations mean the same thing. As for style or format, it is necessary to know in what style or format your dissertation/thesis should be written. There is certain number of formats; some of them are widely used for academic paper writing others are mostly used for publications of different papers on different subjects. So, the main different between formats is the sphere to which your dissertation belongs. It can be either Arts or Sciences. The sphere of Arts has it sown specific formats or styles of academic paper writing. The same can be said about the sphere of Science. There is also one more small division, which is connected to the Legal sphere, but legal papers can also be written in one of formats from the sere of Arts or Sciences.
In general, for writing academic paper the following formats or styles are used: Chicago style, Turabian style, MLA style, Harvard style, Vancouver style and APA style. You can find special guidelines, which are dedicated to each of these formats, and there you can write about peculiarities of each format. The main difference of all these styles is the order of usage citations, punctuation, references, foot-notes, and other similar things. Some formats have many similar features, but each of them also has certain differences. So, before writing your dissertation/thesis it is recommended to find out the dissertation/thesis format. If you begin to write in other format, then you will spend a lot of time making changes. It is very annoying work to check out dissertation looking for mistakes.