Annotation

(n.) A note, added by way of comment, or explanation; -- usually in the plural; as, annotations on ancient authors, or on a word or a passage.

Thesaurus Entries

adversaria, aide-memoire, apparatus criticus, comment, commentary, commentation, docket, entry, exegesis, footnote, gloss, item, jotting, marginal note, marginalia, memo, memoir, memorandum, memorial, minutes, notation, note, note of explanation, register, registry, reminder, scholia, scholium, word of explanation