In typesetting, widows and orphans are lines at the beginning or end of a paragraph, which are left dangling at the top or bottom of a column, separated from the rest of the paragraph. There is some disagreement about the definitions of widow and orphan; what one source calls a widow another calls an orphan.The Chicago Manual of Style uses these definitions:
Donald Knuth, the creator of the TeX computer-typesetting system, calls an orphan a club line.
A common mnemonic is "An orphan has no past; a widow has no future" or "An orphan is left behind, whereas a widow must go on alone".
Another way to think is that orphaned lines appear at the "birth" (start) of paragraphs; widowed lines appear at the "death" (end) of paragraphs.
Alternatively, here's one more mnemonic device: "An orphan is alone from the beginning; a widow is alone at the end," or "An orphan starts alone, a widow ends alone."
Writing guides, such as the Chicago Manual of Style, generally suggest that a manuscript should have no widows and orphans even if the result of avoiding them is additional space at the bottom of a page or column. However, in its 16th edition (2011) the Chicago Manual of Style suggests a new convention in which pages may end with the first line of a new paragraph.
Some techniques for eliminating widows include:
An orphan is cured more easily, by inserting a blank line or forcing a page break to push the orphan line onto the next page to be with the rest of its paragraph. Such a cure may have to be undone if editing the text repositions the automatic page or column break.
Similarly, a single orphaned word at the end of a paragraph can be cured by forcing one or more words from the preceding line into the orphan's line. In web-publishing, this is typically accomplished by concatenating the words in question with a non-breaking space and, if available, by utilizing the orphans: and widows: attributes in Cascading Style Sheets. Sometimes it can also be useful to add non-breaking spaces to the first two (or few) short words of a paragraph to avoid that a single orphaned word is placed to the left or right of a picture or table, while the remainder of the text (with longer words) would only appear after the table.
Most full-featured word processors and page layout applications include a paragraph setting (or option) to automatically prevent widows and orphans. When the option is turned on, an orphan is forced to the top of the next page or column; and the line preceding a widow is forced to the next page or column with the last line.