Widows
A widow is a single short line of text (often the last line of a paragraph) that appears at the top of a new column or page. Widows break visual rhythm and are considered a typographic flaw to be corrected through rewording or adjustment.
In Practice
A widow is a single word or very short line that falls at the end of a paragraph, isolated from the rest of the text by a page or column break. Widows look awkward and break the reading rhythm. The CSS orphans property controls how many lines must appear before a break; widows controls how many lines must appear after. Setting both to 3 or 4 prevents isolated lines at either end of a paragraph.
Common Mistakes
The common mistake with most typographic terms is applying them without considering how they interact with other settings. Type is a system: changing kerning affects tracking, changing size affects leading, changing measure affects line-height. Test changes in context rather than in isolation.
Widows and the two-line fix
A widow is the single short last line of a paragraph that gets pushed onto the next page or column on its own. It looks like a mistake, because one lonely word or phrase carries trailing whitespace across the whole width of the column. Widows appear most often in print pagination and PDF exports, and on the web they mostly surface in fixed-height cards and print stylesheets.
Modern browsers can rewrite the wrapping to avoid them: text-wrap: balance evens out heading lines, and text-wrap: pretty asks the browser to avoid orphans and widows in body copy. The older fix is editorial: reword the paragraph or adjust the width until the last line carries at least two words. For headings that end with a short word like a or the, a non-breaking space between the final words keeps the line complete.