Number sign is the Unicode preferred name for the glyph or symbol #.

It is so used in the United States and Canada, where No. would be used in the United Kingdom (and also Canada since the influence comes from both directions).

The number sign's Unicode value is 0023 in hexadecimal and its ASCII value is 23 in hexadecimal.

It has many other names (and uses) in English. (Those in bold are listed as alternative names in the Unicode documentation.)

• comment sign
  • from its use in some programming languages, e.g. Perl, to introduce comment text
• crosshatch
  • resemblance
• crunch
  • ?
• fence, gate, grid, gridlet
  • resemblance
• hash / hash mark / hash sign
  • the most common name outside the US, including in the UK and Australia
  • Used in the UK and Australia on touch-tone telephones – "Please press the hash key"
• hex
  • from its use to denote hexadecimal values in some markup and programming languages
• octothorn
  • William Sherk in 500 Years of New Words (1983), p. 272, has the following entry: "Octothorn, The number sign (#); so called because there are eight points, or thorns, sticking out of it ... ."
• octalthorpe / octothorp / octothorpe
  • See wiktionary:Octothorpe for etymology.
• pig pen
  • resemblance
• pound / pound sign
  • Used as the symbol for the pound avoirdupois in the U.S. (where lb. would be used in the UK and Canada; note that lb. or lbs. is common in the U.S. as well and is used by the general public more often than #). Never called "pound" in the UK, where the term denotes the pound sterling and its symbol (£).
    • Keith Gordon Irwin in, The Romance of Writing, p. 125 says: "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. The business clerk's hurried way of writing the abbreviation appears to have been responsible for the # sign used for pound."
  • Used in the U.S. and Canada on touch-tone telephones – "Please press the pound key"
• sharp
  • resemblance to the glyph used in music notation; so called in the name of Microsoft's new programming language, C#. However Microsoft says at Frequently Asked Questions About C#:
    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".
    Since most fonts don't contain the sharp sign most websites will doubtless continue to use the fallback hash mark. The "music sharp sign" which should be used if available is U+266F (♯).
• splat
  • colloquial term referring to vague resemblance of # to a squashed spider; this term is also used for the asterisk (*), though.
• square
  • often misattributed as the UK name for #, in reference to touch-tone telephones. From the earliest days of # appearing on telephones, it has been called "hash".
  • 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."
• tic-tac-toe (US) / noughts-and-crosses (UK)
  • resemblance to game board
• widget mark

In Internet chatting, this symbol is used to mark the end of an internet chat session, a convention used to say that the chatter is going to type no more.

In a URL the sign is used between the URL of a webpage and a "name" or "id" which defines a position in that webpage, by means of the attribute in a HTML element. A reference from the page itself can start with the number sign, and dispense with the URL of the page.

The pronunciation of # as "pound" is common in the US which can cause confusion. The British Commonwealth has its own, rather more apposite, use of "pound sign". On British keyboards the UK pound currency symbol often replaces #, with # being elsewhere on the keyboard. The US usage derives from an old-fashioned commercial practice of using a # suffix to tag pound weights on bills of lading. The character is usually called "hash" outside the US.

In other languages

• Bulgarian: диез, pronounced dies
• Chinese: "井號" (jǐng hào; literally: "well" sign) as it resembles the hanzi for water well (井; jǐng)
• Danish: firkant (square), the official name used by telcos for touch-tone key, or havelåge (garden gate from the gate in a picket fence)
• Dutch: hekje (picket fence)
• French: dièse (sharp sign)
• German: Lattenzaun (picket fence), Doppelkreuz (double cross), Raute or Rautenzeichen (the official name used by telcos for touch-tone key)
• Greek: δίεση (diesis)
• Hebrew: sulamit (from sulam == "ladder" + -it, feminine ending)
• Italian: cancelletto (small gate)
• Japanese: "番号記号" (literally: number sign); "井桁" (literally: well curb) or "シャープ" (sharp in hiragana)
• Norwegian: firkant (square)
• Portuguese: cardinal
• Romania: diez ("sharp sign")
• Russian: reshetka, pronounced ree-SHOT-ka (grid)
• Swedish: fyrkant (square)
• Turkish: Sayı işareti

See also

• Numero sign

References (as numbered above)

1. Weird Words
   • Entry for this symbol: http://www.quinion.com/words/weirdwords/ww-oct1.htm – valid as of May 22, 2003
2. World Heritage Dictionary
   • Entry for this symbol: http://www.bartleby.com/61/88/O0028850.html – valid as of May 22, 2003