I'm writing a technical book, and I want to split my book up into about 3 to 6 very broad sections, each of which would have several chapters in it. Is there a standard name for these broad pieces that are bigger than a chapter? Unit? Part? Section?

  • I think your first guess is the best, and the one I've seen most often in technical books-- Unit I, Unit II, etc. Keep the chapter numbering consecutive though; don't start over in a new unit. So Unit I might contain chapters 1-3, and Unit II might have chapters 4-6. Sounds good to me. "Part" is also apt and common. But there's no hard and fast rules-- pick what you think sounds best. Zebra I, Zebra II... Commented Apr 11, 2012 at 4:30
  • Users might be curious to review this link on wikipedia also: en.wikipedia.org/wiki/Book_design Sections are usually used as part of a chapter, not the other way around. Commented Jan 12, 2015 at 0:20

4 Answers 4


Usually it's called a part. A section is typically a cohesive chunk within a chapter. Nobody would know what "unit" means.

But grab a handful of big-ish technical books to see what they call the chunks.

  • Section would work, too.
    – staticsan
    Commented Apr 11, 2012 at 4:26
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    I went through about 15 technical books that I have, and 12 of them don't have anything larger than a chapter. So perhaps that means the "standard" approach is to just stick with chapters. Of the other three, two used "part" and one used "chapter" as the big sections with "item" being used for things that in most other books would have been called a chapter. I suspect that one is very unique in that aspect. While 2/3 isn't that broad of a sampling, perhaps it gives some credence to your point.
    – rbwhitaker
    Commented Apr 11, 2012 at 9:15
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    I vote for "part." "Unit" is for a textbook. Commented Apr 11, 2012 at 10:03
  • 2
    "Part" is what I'm used to. A section is smaller than a chapter. (As one bit of evidence, the DocBook DTD calls for part - chapter - section in that order.) Commented Apr 11, 2012 at 15:05
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    I have the impression that technical writing that follows a public DTD (versus in-house conventions, document styles, etc) is still a minority, but anecdotally, within that set DocBook seems reasonably common. Another reference to chase is DITA, which is more of a framework but has a DTD or schema that people use, I believe. I think FrameMaker SGML had the same structure back when I was using it more than 10 years ago, but those memories are swapped out now. Commented Apr 11, 2012 at 19:51

I don't see a big difference between "part" and "section". However, I would suggest something more descriptive than "Part One" or "Section 1". What do the chapters have in common? Why are the grouped together? It helps the reader if you could call them something like "Part One: Networking".

  • I ended up going with "Part", because after looking over a lot of technical books, and getting feedback from here, I discovered that "Part" was used almost everywhere. People seem to use "Section" to refer to things smaller than a chapter. You answer brings up a great point, though, that the parts should be named, not just numbered. +1 for bringing up that point.
    – rbwhitaker
    Commented May 12, 2012 at 21:04

Generally for books, part works, but for a technical book, if each bit can be treated as a single lesson in the topic, then Unit works well.

If they are merely different parts of a whole, and are different sizes, I would stick to part.

  • I think you've got a good point about there being a small difference between "unit" and "part".
    – rbwhitaker
    Commented Apr 11, 2012 at 9:16
  • In my experience "unit" is only used with training materials (or textbooks). Commented Apr 11, 2012 at 15:07
  • @MonicaCellio - yes, but if the book as a technical one can be used to do self-learning or such like, it makes sense. This even applies if the main usage is for reference, or bedtime reading. Commented Apr 12, 2012 at 10:40
  • I don't think "unit" in a tutorial would be out of place, but it would strike me as odd in a reference manual (something not designed to be read sequentially). But this could vary by domain, so it's best to see what others are doing with documents similar to yours. The people reading yours will probably have read theirs, after all, and that's a source of reader expectations. Commented Apr 12, 2012 at 15:31

What would they be called, besides "section" which seems perfectly fine?

I suggest deploying modernist systematization, especially if that would be considered egregious for your project. For example, you might model your book as a human body, with each 'part' or 'section', here termed 'organ', with the specific organ HEART or FOOT* correlating in some symbolically mystical fashion with the contents of the chapter.

*(Don't be afraid to cheat at your own weird game!)

Note that the body has been done explicitly (as part of the explicit structure) and secretly (on the part of the author) in literary fiction as well as nonfiction extensively.

Which should encourage any technical writer worried that this might be egregious.

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