"Widows" and "orphans" are often referred to when learning about page layout and typography. The two concepts are related, as both are terms for abandoned lines on a page. A widow is abandoned text at the end of a paragraph, while orphans are abandoned text at the beginning of a paragraph.
Before word processors began automatically adjusting typographical page layouts, individuals had to maintain the look of their typed or printed pages themselves. This meant keeping margins clean, making sure that paragraphs were spaced properly, and avoiding problems such as "widow" and "orphan" lines. Both of these concepts refer to unsightly single lines on one page that begin or end a paragraph on another.
So what is a widow in typography? A widow is a line that ends a paragraph and is abandoned at the beginning of a new page. The bulk of the paragraph is located on the previous page. The window line has been abandoned at the end of the paragraph. Widow lines can be confusing because they cause a disruption in the paragraph. They often contain only a few words so they appear to be short and ill-formed sentences.Depending on how the line is formed, readers may have to back-track once they have finished the paragraph to make sure that they understand it correctly.
An orphan is essentially the opposite of a widow. It is a single line at the bottom of a page which finishes a paragraph that continues on the next page. Similar to a widow line, an orphan line is so named because it is separated from what comes after it. The mneumonic device used to remember this is "An orphan has no past; a widow has no future."
Orphans are undesireable because it can be difficult to tell whether it is a separate sentence or part of the paragraph that begins the next page.
Avoiding Widows and Orphans
Many modern word processors automatically adjust paragraph breaks to avoid the creation of widow and orphan lines in documents. When using a word processor that doesn't adjust paragraph breaks or typing on a typewriter, you will have to do this yourself. Widows and orphans can be avoided in one of two ways, either by moving the abandoned line to the other page with the rest of the paragraph or by breaking the paragraph in such a way that there are two lines left on the page.
Orphans are often easier to move to another page due to the fact that moving them does not make the bottom-page margin shrink. When trying to decide whether to break a paragraph to leave two lines on the page or to move a widow or orphan, take this margin into account: You want to keep the bottom margin consistent on all of your pages, typically leaving at least an inch of white space. Break the paragraph if moving the widow or orphan would infringe on the lower margin, or take the action you prefer if the margin will not be affected.
- Wikipedia - Widows and Orphans: http://en.wikipedia.org/wiki/Widows_and_orphans