Marginalia

Marginalia (plurale tantum) is the general term for notes, scribbles, and editorial comments made in the margin of a book. The term is also used to describe drawings and flourishes in medieval illuminated manuscripts. True marginalia is not to be confused with reader's signs, marks (e.g. stars, crosses, fists) or doodles in books. The formal way of adding descriptive notes to a document is called annotation.