Widows, orphans, running heads and the other things a typesetter fixes
Widows and orphans
A paragraph that is split across two pages can leave a single line stranded. If the stranded line is the paragraph's last line sitting at the top of the next page, it is a widow. If it is the first line sitting alone at the bottom of a page, it is an orphan. A one-word last line of a paragraph is sometimes called a runt, and it becomes a widow if the page breaks before it.
Why it matters: a lone line at the top of a page looks like a mistake, and a lone line at the bottom makes the reader turn the page mid-thought. Typesetters fix them by pulling a line back or pushing a line forward. That can make a page one line short or one line long; the fix is to do the same to the facing page so the spread still balances.
Word processors have a "widow/orphan control" checkbox that keeps at least two lines together. It works, but it only ever moves lines forward, which leaves short pages with no attempt to balance the spread.
Running heads and page numbers
The line at the top of each page is the running head. Convention puts the author's name on the left-hand page (the verso) and the book title or chapter title on the right-hand page (the recto). Page numbers, called folios, go at the outer edge of the running head or centered at the foot of the page.
Three pages do not get a running head or a folio: the first page of a chapter, blank pages, and the display pages at the front (half title, title page, copyright). Chapter openers have a folio only if it is at the foot of the page, and even then it is often dropped. This is the single most common tell of a book formatted in a word processor: a running head sitting above a chapter title.
Front matter is numbered in lowercase roman numerals (i, ii, iii) and the body starts again at 1. The roman numerals are counted but usually not printed on the display pages.
Rectos and versos
Odd-numbered pages are always on the right. That rule decides everything else: the title page is a recto, the copyright page is the verso behind it, the dedication is a recto, and the first chapter starts on a recto, which sometimes means a blank verso before it. When a book is set up with mirrored margins, the inside margin is on the left of a recto and on the right of a verso.
Chapter openers
A chapter starts lower on the page than the text on other pages. This gap, the sink or chapter drop, is usually a third of the way down. The first paragraph is not indented, because there is nothing above it to separate it from. Many books mark the opening with a drop cap (a large first letter set into two or three lines) or by setting the first few words in small capitals.
Paragraphs
Fiction indents the first line of each paragraph and puts no space between paragraphs. Non-fiction often does the opposite: no indent and a half-line of space. Never both. The indent is small, about one em, which is the width of the type size. A half-inch tab, the word-processor default, is far too much for a 6×9 page.
Body text is justified, flush to both margins, with hyphenation on. Without hyphenation, justified text develops rivers, the white gaps that run down a paragraph where the spaces stretched. A typesetter also avoids more than two or three hyphenated lines in a row.
Scene breaks
A break between scenes inside a chapter is marked with a blank line, or with an ornament centered in it: three asterisks, an asterism ⁂, a fleuron ❧, a short rule. A blank line alone disappears when it falls at the bottom of a page, so if you use one, the paragraph after it is often set without an indent so the break remains visible. An ornament survives a page break.
Type and leading
Books are set in a serif typeface at a size between 10 and 12 points, with leading (line spacing) of roughly 1.3 to 1.45 times the type size. Lines should hold about 60 to 70 characters; longer than that and the eye loses its place on the return. That is why margins matter as much as type size: on a 6×9 page, a 4.5-inch measure with 11-point Garamond comes out right.
Straight quotes (") and apostrophes (') are replaced with curly ones (“ ” ’). Two hyphens become an em dash. A run of periods becomes an ellipsis character. These are small, and they are everywhere on the page.
Notes
Footnotes sit at the bottom of the page they belong to, separated by a short rule, in a smaller size. Endnotes collect at the end of the chapter or the book. Fiction rarely has either; non-fiction usually chooses one and sticks with it. A footnote that does not fit at the foot of its page continues at the foot of the next.
Blank pages and the last page
A blank page is completely blank: no running head, no folio. Print-on-demand books need an even page count, so the printer adds a blank at the end if needed. Some publishers use the last verso for an "About the author" page or a list of other titles so the book does not end on a blank.
Questions
What is the difference between a widow and an orphan?
A widow is the last line of a paragraph left alone at the top of a page. An orphan is the first line of a paragraph left alone at the bottom of a page. Both are avoided by moving a line or two, or by letting the page run a line short or long.
Does Amazon KDP reject books for widows and orphans?
No. KDP checks technical things such as margins, embedded fonts and bleed. Widows, orphans, rivers and bad breaks pass review, but readers and reviewers notice them.
Should a chapter always start on a right-hand page?
In traditional publishing, usually yes for the first chapter and often for all of them. Starting every chapter on a recto adds blank left-hand pages, which costs a little in print-on-demand. Many novels now let chapters start on either page. Both are acceptable; be consistent.