footnote

Short definition from Wiktionary

Noun

1. 1
   A short piece of text, often numbered, placed at the bottom of a printed page, that adds a comment, citation, reference etc, to a designated part of the main text.
2. 2
   An event of lesser importance than some larger event to which it is related.
3. 3
   A qualification to the import of something.

Verb

1. 1
   To add footnotes to a text.