Longer writing projects are usually divided up into chapters and include what are known as front matter and back matter as well as the main body of the text. The length of each depends on the size of a project, longer in the case of a book or dissertation, and shorter in the case of a journal article or MA thesis.
Preface: This is usually a short personal essay describing why you wrote the work and how it fits into the genre or discipline it engages. It is present in most book-length works and in MA or PhD theses, but not in shorter works.
Acknowledgements: The purpose of acknowledgements is to thank people or institutions who helped you in your work. Often, if you were supported by grants or institutional funds, you are legally obliged to acknowledge the support. In journal articles, acknowledgements can be placed as the first footnote, and in most scholarly books they form the final section of the Preface.
Introduction: An introduction summarizes in brief the entire project, describing what it covers, how it approaches the topic, and how it is situated with respect to other work in the area.
Bibliography: Appears at the end of a project, and often goes beyond a mere works cited list to include other works you have consulted in your research.
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