A footnote is a small note placed at the bottom of a page that gives extra information about something mentioned in the main text. Writers use footnotes to cite their sources, explain complicated details, or add interesting side points without interrupting the flow of their writing. If you're reading a history book and see a tiny number like this¹ after a sentence, you can look down at the bottom of the page to find the matching footnote with more details.

Footnotes help readers who want to dig deeper or check where information came from. A biography might use footnotes to list which letters or documents proved a certain fact. A science textbook might use them to define technical terms. Sometimes authors tuck amusing comments or fascinating tidbits into footnotes for curious readers who make the effort to look.

The word can also mean something considered minor or insignificant. When someone becomes a footnote in history, they played such a small role that they barely get mentioned. A footnote to a major event is a detail people mostly overlook. This usage captures how actual footnotes sit at the margins of a page, present but not central to the main story.