A widow is the end of a paragraph (a single line of text consisting of one or more words) that appears at the top of a column. An orphan is a single word (or syllable) that sits at the bottom of a paragraph of text.
Additionally, an orphan can refer to the first line of a new paragraph that sits on its own at the bottom of a column of text.
Text with many widows and orphans typically has poor readability, and they should be avoided if possible. They occur frequently when setting long-form text, so it’s useful to know how to tackle them when they arise. See our article “Avoiding widows & orphans” for more information.