I'm in the process of writing a dissertation for my university degree.
I have looked at examples online where people have used Roman numerals as page numbers for the preliminary pages of the dissertation and then Arabic numbers for the main text pages.
Why does this happen? Does it not cause confusion having two different sets of numbers? I've seen this in a couple of books and not just in university dissertations.
Translator's notes, prefaces, and introductions are numbered using Roman numerals so those pages can be safely cited without duplication or ambiguity.
It is customary to number the primary text with Arabic numbers starting at 1. But as the front matter is clearly 'before' page 1, you have to make accommodations for it in your numbering scheme. A new set of independently numbered Roman numerals are used to differentiate the two groups of pages. This allows both sets to 'start' at 1 (or i) without duplication. Also note that Roman numerals are always italicized. In contrast, end matter tends to continue the numbering of the primary text. Sometimes end matter is not numbered because it is short, rarely cited, or can be referenced in another way (i.e. 'footnote 31', or 'appendix A', or 'postscript').
There are some quite old standards for the ordering of front and back matter: Book design | Wikipedia. This Wikipedia page is the most comprehensive list of these rules that I've found online. However, some of these rules are more rigid than others so you can stray from them if you have a compelling reason specific to your project.
An excellent guide to print design is Bringhurst's book The Elements of Typographic Style. It is an authority for designers and commonly recommended as an introduction. It has a fair bit of history and explanation as to why these rules exist, but is mostly for designers and typographers.
If you just want formatting 'rules' beyond the Wikipedia page, then see Turabian's A Manual for Writers of Research Papers, Theses, and Dissertations, Eighth Edition: Chicago Style for Students and Researchers. (Affectionately shortened as 'Turabian'.) The book itself is a greatly condensed version of the monolithic Chicago Manual of Style (CMoS). Note that while 'Chicago' style citations are standard for most humanities and social sciences, some disciplines (mostly scientific) use other style guides like APA or MLA. All this is covered in Turabian.
Answer on the purpose:
"Front-matter pages are traditionally numbered in lower-case Roman numerals (i, ii, iii, iv, v, etc.), which prevents renumbering the remainder of a book when front-matter content is added at the last moment, such as a dedication page or additional acknowledgments."
(source: https://en.wikipedia.org/wiki/Book_design)
"The front matter of a book is paginated with lowercase roman numerals (see 1.4). This traditional practice prevents renumbering the remainder of a book when, for example, a dedication page or additional acknowledgments are added at the last moment."
(Source: The Chicago manual of style. 17th ed. London;Chicago;: The University of Chicago Press; 2017.)
My opinion: the emphasis is on 'traditional'; it is an old (outdated, but not by usage) practice which makes no sense anymore, when works are published as PDFs using word or latex, where page numbering is automatically adjusted after including new front matter. -- I never used it in my theses so far and I will try my best to avoid it in the future; because so far I found it only confusing and not helpful, rather detrimental when dealing with non-fiction. (I often asked myself: if intro or preface are not numbered, are they not important for the work? and often, the work starting from '1' makes only good sense when the preface or intro from III-XI e.g. is read/included. so why exclude it from the main body of work/text by using roman numerals? and why lowercase numerals? makes it even worse. -- I only see reason in using roman numerals for the pages by the publisher, which are not part of the author's actually work. but if I put contents and a quote and a preface there, carrying important 'intro-info' for my work, then I want them part of the work, thus using Arabic numerals.)
Roman numerals are usually used for the preface, introducion, contents page, etc. Arabic numbers are used for the actual text of the book. One is used for extras and the other is used for the actual text.
