Number sign

Not to be confused with the Chinese character , the sharp sign (), the viewdata square (), the numero sign (), the equal and parallel to symbol () or the game Tic-tac-toe's grid.
Number sign

The symbol # is most commonly known as a number sign, hash,[1] or pound sign.[2] Other names include octothorpe and hashtag. The symbol is used for a variety of purposes, including the designation of a number (for example, "#1" represents "number one"), an abbreviation for pounds avoirdupois, a metadata tag on social media platforms,[3] and a button on touch-tone telephones. The symbol is defined in Unicode and ASCII as U+0023 # NUMBER SIGN (HTML #).

The musical symbol called sharp () is different and has a different Unicode assignment. A sharp cannot have horizontal lines (to avoid being obscured by the horizontal musical staff lines), while in most fonts the number sign has horizontal lines.

Origin and names

A stylized version of the abbreviation for libra pondo, ℔.
The abbreviation written by Isaac Newton.

It is often claimed that the symbol traces its origins to the symbol ℔, an abbreviation of the Roman term libra pondo, which translates as "pound weight".[4][5] This abbreviation was printed with a dedicated ligature type, with a horizontal line across, so that the lowercase letter "l" would not be mistaken for the numeral "1": ℔. Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two forward-slash-like strokes "//".[5]

The symbol is described as the "number" character in an 1853 treatise on book-keeping.[6] Examples of it being used to indicate pounds exist at least as far back as 1850,[7] and its double meaning is described in a book-keeping text from 1880.[8] The symbol appears to be used primarily in handwritten material, while in the printing business, the numero (№) symbol and barred-lb (℔) are used for "number" and "pounds" respectively. It appeared on the keyboard of the Remington Standard typewriter (c. 1886),[9] but was not used on the keyboards used for typesetting.[7] The instruction manual of the Blickensderfer model 5 (c. 1896) appears to refer to the symbol as the "number mark".[10] Some early twentieth-century U.S. sources refer to it as the "number sign",[11] although this could also refer to the numero sign.[12]

A 1917 manual distinguishes between two uses of the sign: "number (written before a figure)" and "pounds (written after a figure)".[13] The use of the phrase "pound sign" to refer to this symbol is found from 1932 in U.S. usage.[14] Before this time, and still outside the U.S., the term "pound sign" was used to refer to the pound currency symbol (£) or the pound weight symbol (lb).

An alternative theory is that this name arose from the fact that character encodings used the same code for both the number sign and the British pound sign "£". Claims have included ISO 646-GB as well as the Baudot code in the late 19th century.[15] The apparent use of the sign to mean pounds weight in 1850[7] appears to rule out both of these code sets as the origin, though that same reference admits that the earliest reference in print was a decade after Baudot code.

"Hash sign" is found in South Africans writings from the late 1960s,[16] and from other non-North-American sources in the 1970s.

Usage in North America

Mainstream use in the United States is as follows: when it prefixes a number, it is read as "number", as in "a #2 pencil" (indicating "a number-two pencil"). When the symbol follows a number, the symbol indicates weight in pounds. (Five pounds are indicated as 5#.) This traditional usage still finds handwritten use, and may be seen on some signs in markets and groceries. It is also commonly known as the "pound sign".[17]

In Canada the symbol is called both the "number sign" and the "pound sign".[18] The American company Avaya have an option in their programming to denote Canadian English, which in turn instructs the system to say "number sign" to callers instead of "pound sign".[19]

Usage in the United Kingdom and Ireland

In the United Kingdom and Ireland, it is generally[20] called a hash (probably ultimately from "hatch",[21] referring to cross-hatching, although the exact derivation is disputed[22]). It is never used to denote pounds weight (lb or lbs is used for this) or pounds sterling (for which "£" is used). It is never called the "pound sign", because that term is understood to mean the currency symbol "£", for pound sterling or (formerly) Irish pound.

The use of "#" as an abbreviation for "number" is often understood in Britain and Ireland, especially where there has been business or educational contact with American usage, but use in print is rare[23] and British typewriters had "£" in place of the American "#".[24] Where Americans might write "Symphony #5", the British and Irish are more likely to write "Symphony No. 5", or perhaps use the numero sign "Symphony № 5" (as in The New Grove Dictionary of Music and Musicians).

To add to the confusion between "£" and "#", in BS 4730 (the UK national variant of the ISO/IEC 646 character set), 0x23 represents "£" whereas in ASCII (the US variant), it represents "#". It was thus common, when systems were incorrectly configured, for "£" to be displayed as "#" and vice versa.

Other names in English

The symbol has many other names (and uses) in English:

Comment sign 
Taken from its use in many shell scripts and some programming languages (such as Python) to start comments.
In China, non-native English speakers often refer to the number sign as "cross". It is said as jĭng in Chinese, as it looks like the Chinese character for water well ("井").
Hashtag, hashtag symbol
Twitter documentation refers to it as "the hashtag symbol"[25] The word "hashtag" is often used when reading social media messages aloud. For instance the text "#xyz" is often read out loud as "hashtag, x, y, z" (as opposed to "hash, x, y, z" or "number sign, x, y, z").
Common usage in Singapore and Malaysia, as spoken by many recorded telephone directory-assistance menus: "Please enter your phone number followed by the hex key". The term "hex" is discouraged in Singapore in favour of "hash". In Singapore, a hash is also called "hex" in apartment addresses, where it precedes the floor number.[26][27]
Octothorp, octothorpe, octathorp, octatherp
Most scholars believe the word was invented by workers at the Bell Telephone Laboratories by 1968,[28] who needed a word for the symbol on the telephone keypad. Don MacPherson is said to have created the word by combining octo and the last name of Jim Thorpe, an Olympic medalist.[29] Howard Eby and Lauren Asplund claim to have invented the word as a joke in 1964, combining octo with the syllable therp which, because of the "th" diphthong, was hard to pronounce in different languages.[30] The Merriam-Webster New Book of Word Histories, 1991, has a long article that is consistent with Doug Kerr's essay[31] which says "octotherp" was the original spelling, and that the word arose in the 1960s among telephone engineers as a joke. Other hypotheses for the origin of the word include the last name of James Oglethorpe,[32] or using the Old English word for village, thorp, because the symbol looks like a village surrounded by eight fields.[33][34] The word was popularized within and outside Bell Labs.[35] The first appearance of "octothorp" in a US patent is in a 1973 filing. This patent also refers to the six-pointed asterisk (✻) used on telephone buttons as a "sextile".[36]
Resemblance to the glyph used in music notation, U+266F (♯). So called in the name of the Microsoft programming languages C#, J# and F#. However Microsoft says "It's not the 'hash' (or pound) symbol as most people believe. It's actually supposed to be the musical sharp symbol. However, because the sharp symbol is not present on the standard keyboard, it's easier to type the hash ('#') symbol. The name of the language is, of course, pronounced 'see sharp'."[37] According to the ECMA-334 C# Language Specification, section 6, Acronyms and abbreviations, the name of the language is written "C#" ("LATIN CAPITAL LETTER C (U+0043) followed by the NUMBER SIGN # (U+0023)") and pronounced "C Sharp".[38]
Used in proof-reading to denote that a space should be inserted. This can mean
  1. a line space (the space between two adjacent lines denoted by line # in the margin),
  2. a hair space (the space between two letters in a word, denoted by hr #)
  3. a word space, or letter space (the space between two words on a line, two letter spaces being ##)
Em- and en-spaces (being the length of a letter m and n, respectively) are denoted by a square-shaped em- or en-quad character (⊞ and ⊟, respectively).
Occasionally used in the UK (e.g. sometimes in BT publications and automatic messages) – especially during the Prestel era, when the symbol was a page address delimiter. The International Telecommunications Union specification ITU-T E.161 3.2.2 states: "The # is to be known as a 'square' or the most commonly used equivalent term in other languages."
crosshatch, (garden) fence, mesh, flash, grid, pig-pen, tictactoe, scratch (mark), (garden) gate, hak, oof, rake, crunch, punch mark,[39] sink, corridor, capital 3, and waffle.

In mathematics

In computing

Other uses


In Unicode, several # characters are assigned:

In other languages or scripts:

Related characters, the sharp sign in musical notation:

In mathematics, the equal and parallel to sign:

On keyboards

On the standard US keyboard layout, the # symbol is ⇧ Shift+3. On standard UK and some other European keyboards, the same keystrokes produce the pound currency symbol (£), and # is moved to a separate key above the right shift. On UK Mac keyboards, # is generated by ⌥ Opt+3, whereas on other European Mac keyboards, the # can be found above the right shift key.

See also


  1. Nicks, Denver (June 13, 2014). "You'll Never Guess the Real Name for a Hashtag". TIME. Retrieved May 5, 2016.
  2. "pound sign, n.". Oxford English Dictionary. Retrieved 5 May 2016.
  3. Piercy, Joseph (25 October 2013). Symbols: A Universal Language. Michael OMara. pp. 84–85. ISBN 978-1-78243-073-5. Retrieved 4 October 2014.
  4. "The Italian libbra (from the old Latin word libra, 'balance') represented a weight almost exactly equal to the avoirdupois pound of England. The Italian abbreviation of lb with a line drawn across the letters [℔] was used for both weights." Keith Gordon Irwin, in The Romance of Writing, p. 125 The Unicode character U+2114 L B BAR SYMBOL (HTML ℔) is intended to represent this ligature.
  5. 1 2 Houston, Keith (2013-09-06). "The Ancient Roots of Punctuation". The New Yorker. Retrieved 16 October 2013.
  6. Crittendon, S. W. (1853). An Elementary Treatise on Book-keeping by Single and Double Entry. Philadelphia: E., C., & J. Biddle. p. 10. Retrieved 24 November 2015.
  7. 1 2 3 "The Sign of the Number". Sentence Spacing. Retrieved 24 November 2015.
  8. Duff, C. P.; Duff, W. H.; Duff, R. P. (1880). Book-Keeping By Single and Double Entry. Harper and Brothers. p. 21. Retrieved 24 November 2015.
  9. "Remington Standard typewriter". New York: Wyckoff, Seamans & Benedict. 1886. p. 50.
  10. n.a. (1896). Method of Operating and Instructions for Practice on the Blickensderfer Typewriter (PDF). Atlanta, GA,: K. M. Turner. p. 14. It is best to use the "number mark" for plus; the hyphen for minus, and two hyphens for the sign =
  11. e.g. J. W. Marley, "The Detection and Illustration of Forgery By Comparison of Handwriting", in Proceeedings of the Sixteenth Annual Convention of the Kansas Bankers' Association. Kansas City: Rusell. 1903. p. 180.
  12. e.g. The British Printer vol. viii (1895), p. 395
  13. Thurston, Ernest L. (1917). Business Arithmetic for Secondary Schools. New York: Macmillan. p. 419.
  14. Lawrence, Nancy M.; F. Ethel McAfee; Mildred M. Butler (1932). Correlated studies in stenography. Gregg. p. 141.
  15. "The "pound sign" mystery". Retrieved 22 December 2012.
  16. Research Review. Navorsingsoorsig vols. 18-21, pp. 117, 259 (1968)
  17. William Safire (March 24, 1991). "On Language; Hit the Pound Sign". New York Times. Retrieved May 21, 2011.
  18. Barber, edited by Katherine (2004). The Canadian Oxford dictionary (2nd ed.). Toronto: Oxford University Press. ISBN 0195418166.
  20. "How the # became the sign of our times". The Guardian. Retrieved 30 December 2014.
  21. "Hash sign". Oxford English Dictionary. Retrieved 14 October 2013.
  22. "Britain on Hash". Sentence Spacing. Retrieved 24 November 2015.
  23. "Google Ngram Viewer".
  24. "The Hashtag: A History Deeper than Twitter". Retrieved 30 December 2014.
  25. "Using hashtags on Twitter". Twitter. Retrieved 5 May 2016.
  26. Jack Tsen-Ta Lee. "A Dictionary of Singlish and Singapore English". Retrieved 14 January 2016.
  27. "Address Formats". Retrieved 14 January 2016.
  28. Hochhester, Sheldon (2006-09-29). "Pressing Matters: Touch-tone phones spark debate" (PDF). Encore.
  29. Ralph Carlsen, "What the ####?" Telecoms Heritage Journal 28 (1996): 52-53.
  30. Kerr, "The ASCII Character 'Octatherp.'"
  31. Douglas A. Kerr (2006-05-07). "The ASCII Character "Octatherp"" (PDF).
  32. John Baugh, Robert Hass, Maxine H. Kingston, et al, "Octothorpe," The American Heritage Dictionary of the English Language (Boston: Houghton Mifflin, 2000)
  33. Quinion, Michael (19 May 2010). "Octothorpe". World Wide Words. Retrieved 10 May 2016.
  34. Bringhurst, "Octothorpe". Elements of Typographic Style
  35. "You Asked Us: About the * and # on the New Phones," The Calgary Herald, September 9, 1972, 90.
  36. "U.S. Patent No. 3,920,296". Retrieved 16 September 2014.
  37. "Frequently Asked Questions about C#". Retrieved 16 September 2014.
  38. "". Retrieved 16 September 2014.
  39. "Pronunciation guide for Unix - Bash -". Retrieved 16 September 2014.
  40. "Introduction to HTML". Retrieved 16 September 2014.
  41. "". Retrieved 16 September 2014.
  42. "". Retrieved 16 September 2014.
  43. Nicks, Denver (13 June 2014). "You'll Never Guess the Real Name for a Hashtag". TIME. Retrieved 6 May 2016.
  44. "How to Format a Press Release for the Associated Press", wikiHow
  45. "Scrabble Glossary". Tucson Scrabble Club. Retrieved 2012-02-06.
  46. Glossary of Medical Devices and Procedures: Abbreviations, Acronyms, and Definitions
  47. Carnie, Andrew (2006). Syntax: A Generative Introduction (2nd ed.). Oxford: Wiley-Blackwell. ISBN 1-4051-3384-8.
  48. Vicars, Bill. "Lexicalization". ASL University. Retrieved 6 September 2015.
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