#marginal note

• Annotation — The act of annotating and its result; a note, observation, or explanatory comment written on the margin of a text or at the footnote of a page to clarify, complete, or interpret an item of information. It represents an essential philological and didactic tool in the critical study of documents or the structural organization of study materials.
• Annotation — A note, explanatory record, gloss, or short critical comment written on the margin of a text, manuscript, or historical document to clarify a term, passage, or the work's context; the result of the act of annotating. In computational linguistics, it denotes a structural label attached to a text unit to assign a formal meaning to it.