Marginalia is a plural noun that refers to notes or other marks written in the margins of a text, and also to nonessential matters or items.

// I loved flipping through my literature textbooks to find the marginalia left behind by former students.

// She found the documentary's treatment of not only the major events but also the marginalia of Scandinavian history fascinating.

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“Marginalia have a long history: Leonardo da Vinci famously scribbled thoughts about gravity years before Galileo Galilei published his magnum opus on the subject; the discovery was waiting under our noses in the margins of Leonardo’s Codex Arundel.” — Brianne Kane, Scientific American, 19 Sept. 2025

In the introduction to his essay titled “Marginalia,” Edgar Allan Poe wrote: “In getting my books, I have always been solicitous of an ample margin; this not so much through any love of the thing in itself, however agreeable, as for the facility it affords me of penciling suggested thoughts, agreements and differences of opinion, or brief critical comments in general.” At the time the essay was first published in 1844, marginalia was only a few decades old despite describing something—notes in the margin of a text—that had existed for centuries. An older word, apostille (or apostil), refers to a single annotation made in a margin, but that word is rarely used today. Even if you are not, like Poe, simply ravenous for scribbling in your own books, you likely know marginalia as a telltale sign that someone has read a particular volume before you.