A note is a string of text placed at the bottom of a page in a book or document or at the end of a chapter, volume or the whole text. The note can provide an author's comments on the main text or citations of a reference work in support of the text, or both. A footnote is normally flagged by a superscripted number immediately following that portion of the text the note is in reference to.
- The first idea1 for the first footnote on the page, the second idea2 for the second footnote, and so on.
Occasionally a number between brackets or parentheses is used instead, thus: . Typographical devices such as the asterisk (*) or dagger (†) may also be used to point to footnotes; the traditional order of these symbols is *, †, ‡, §, ‖, ¶. In documents like timetables, many different symbols, as well as letters and numbers, may be used to refer the reader to particular notes.
In Arabic texts, a specific Arabic footnote marker (), encoded at code point U+0602 in Unicode, is also used.
Footnotes are notes at the foot of the page while endnotes are collected under a separate heading at the end of a chapter, volume, or entire work. Unlike footnotes, endnotes have the advantage of not affecting the layout of the main text, but may cause inconvenience to readers who have to move back and forth between the main text and the endnotes.
Academic usage 
Notes are most often used as an alternative to long explanatory notes that can be distracting to readers. Most literary style guidelines (including the Modern Language Association and the American Psychological Association) recommend limited use of foot and endnotes. However, publishers often encourage note references in lieu of parenthetical references. Aside from use as a bibliographic element, notes are used for additional information or explanatory notes that might be too digressive for the main text.
In particular, footnotes are the normal form of citation in historical journals. This is due, firstly, to the fact that the most important references are often to archive sources or interviews which do not readily fit standard formats, and secondly, to the fact that historians expect to be see the exact nature of the evidence which is being used at each stage.
The MLA (Modern Language Association) requires the superscript numbers in the main text to be placed following the punctuation in the phrase or clause the note is in reference to. The exception to this rule occurs when you have a hyphen in a sentence, in which case the superscript would appear before.
Aside from their technical use, authors use notes for a variety of reasons:
- As signposts to direct the reader to information the author has provided or where further useful information is pertaining to the subject in the main text.
- To attribute to a quote or viewpoint.
- As an alternative to parenthetical references; it is a simpler way to acknowledge information gained from another source.
- To escape the limitations imposed on the word count of various academic and legal texts which do not take into account notes. Aggressive use of this strategy can lead the text to be seen as affected by what some people call "foot and note disease."
Literary device 
At times, notes have been used for their comical effect, or as a literary device.
- J.G. Ballard's "Notes Towards a Mental Breakdown," is one sentence ("A discharged Broadmoor patient compiles 'Notes Towards a Mental Breakdown,' recalling his wife's murder, his trial and exoneration.") and a series of elaborate footnotes to each one of the words.
- Mark Z. Danielewski's House of Leaves uses what are arguably some of the most extensive and intricate footnotes in literature. Throughout the novel, footnotes are used to tell several different narratives outside of the main story. The physical orientation of the footnotes on the page also works to reflect the twisted feeling of the plot (often taking up several pages, appearing mirrored from page to page, vertical on either side of the page, or in boxes in the center of the page, in the middle of the central narrative).
- Flann O'Brien's The Third Policeman utilizes extensive and lengthy footnotes for the discussion of a fictional philosopher, de Selby. These footnotes span several pages and often overtake the main plotline, and add to the absurdist tone of the book.
- David Foster Wallace's Infinite Jest includes over 400 endnotes, some over a dozen pages long. Several literary critics suggested that the book be read with two bookmarks. Wallace uses footnotes in much of his other writing as well.
- Manuel Puig's Kiss of the Spider Woman (originally published in Spanish as El beso de la mujer araña) also makes extensive use of footnotes.
- Garrison Keillor's Lake Wobegon Days includes lengthy footnotes and a parallel narrative.
- Mark Dunn's Ibid: A Life is written entirely in endnotes.
- Luis d'Antin van Rooten's Mots d'Heures: Gousses, Rames (the title is in French, but when pronounced, sounds similar to the English "Mother Goose Rhymes"), in which he is allegedly the editor of a manuscript by the fictional François Charles Fernand d’Antin, contains copious footnotes purporting to help explain the nonsensical French text. The point of the book is that each written French poem sounds like an English nursery rhyme.
- Terry Pratchett has made numerous uses within his novels. The footnotes will often set up running jokes for the rest of the novel.
- Susanna Clarke's Jonathan Strange & Mr Norrell uses dozens of footnotes referencing a number of fictional books including magical scholarship and biographies.
- Jonathan Stroud's The Bartimaeus Trilogy uses footnotes to insert comical remarks and explanations by one of the protagonists, Bartimaeus.
- Michael Gerber's Barry Trotter parody series used footnotes to expand one-line jokes in the text into paragraph-long comedic monologues that would otherwise break the flow of the narrative.
- John Green's An Abundance of Katherines uses footnotes in which he says: "[They] can allow you to create a kind of secret second narrative, which is important if, say, you're writing a book about what a story is and whether stories are significant."
- Jasper Fforde's Thursday Next series exploits the use of footnotes as a communication device (the footnoterphone) which allows communication between the main character’s universe and the fictional bookworld.
- Ernest Hemingway's Natural History of the Dead uses a footnote to further satirize the style of a history while making a sardonic statement about the extinction of "humanists" in modern society.
- Pierre Bayle's Historical and Critical Dictionary follows each brief entry with a footnote (often five or six times the length of the main text) in which saints, historical figures, and other topics are used as examples for philosophical digression. The separate footnotes are designed to contradict each other, and only when multiple footnotes are read together is Bayle's core argument for Fideistic skepticism revealed. This technique was used in part to evade the harsh censorship of 17th century France.
- Mordecai Richler's novel Barney's Version uses footnotes as a character device that highlights unreliable passages in the narration. As the editor of his father's autobiography, the narrator's son must correct any of his father's misstated facts. The frequency of these corrections increases as the father falls victim to both hubris and Alzheimer's disease. While most of these changes are minor, a few are essential to plot and character development.
- In Vladimir Nabokov's Pale Fire, the main plot is told through the annotative endnotes of a fictional editor.
- Bartleby y compañía, a novel by Enrique Vila-Matas, is stylized as footnotes to a nonexistent novel.
- The works of Jack Vance often have footnotes, detailing and informing the reader of the background of the world in the novel.
- Stephen Colbert's I Am America (and so Can You!) uses both footnotes and margin notes to offer additional commentary and fourth-wall-breaking humor.
HTML, the predominant markup language for web pages, has no mechanism for marking up notes. Despite a number of different proposals over the years, and repeated pleas from the user base, the working group has been unable to reach a consensus on it. Because of this, MediaWiki, for example, has had to introduce its own
<ref></ref> tag for citing references in notes, an idea which has since also been implemented for generic use by the Nelson HTML preprocessor.
It might be argued that the hyperlink partially eliminates the need for notes, being the web's way to refer to another document. However, it does not allow citing to offline sources and if the destination of the link changes, the link can become dead or irrelevant.
Associate Justice Stephen Breyer of the Supreme Court of the United States is famous in the American legal community for his writing style, in which he never uses notes. He prefers to keep all citations within the text (which is permitted in American legal citation). Richard A. Posner has also written against the use of notes in judicial opinions. Bryan A. Garner, however, advocates using notes instead of inline citations.
See also 
- Robert Bringhurst (2005). The Elements of Typographic Style (version 3.1). Point Roberts, WA: Hartley and Marks. pp 68–69. Bringhurst goes on to say “But beyond the ... double dagger, this order is not familiar to most readers, and never was.”
- "Chapter 15: Footnotes, indexes, contents, and outlines". U.S. Government Printing Office Style Manual. Retrieved January 23, 2010.
- "A Guide to Footnotes and Endnotes for NASA History Authors". NASA History Style Guide. Retrieved March 24, 2005.
- Rogers, Timothy (1968). "Rupert Brooke: Man and Monument". English 17 (99): 79–84. Retrieved 21 March 2011.
- "Nelson HTML Preprocessor". Retrieved 2009-06-09.
- "In Justice Breyer's Opinion, A Footnote Has No Place". The New York Times. 1995-07-28. Retrieved 2008-04-30.
- See Indiana Courts – Footnotes in Legal Opinions