{i} comment or explanation added to a text; comment or remark added to a computerized document (Computers); additional information about a part or feature of a computer program (Computers)
Annotation is the activity of annotating something. She retained a number of copies for further annotation
An annotation is a note that is added to a text or diagram, often in order to explain it. He supplied annotations to nearly 15,000 musical works. = footnote
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