Number sign is a name for the symbol #; it is the preferred Unicode name for the code point associated with that glyph. The symbol is similar to the musical symbol called sharp (♯). Several other names for this symbol are used in the United States and Canada. In most other English-speaking countries, it is called a hash.
The number sign’s Unicode code point is U+0023, and its ASCII value is 0x23 (hexadecimal).
In many parts of the world, including Europe, Canada, Australia, and Russia, “number sign” is the name of the “número” sign № (Unicode code point U+2116), which is often written simply as No. In some of those countries, the # sign is not used to indicate a number.
Usage in North America
The mainstream use in the U.S. is this: when it precedes a number, it is read as "number," as in "a #2 pencil" (spoken as "a number two pencil"); when it follows a number, it is read as "pounds", as in "5# of sugar" (spoken as "five pounds of sugar"). The first form is more common; the second is becoming archaic.
Naming conventions in North America
In some regions of the United States and Canada, the symbol is traditionally called the pound sign, but in others, the number sign. This derives from a series of abbreviations for pound, which is a unit of weight. At first "lb." was used; however, printers later designed a font containing a special symbol of an "lb" with a line through the ascenders so that the lowercase letter "l" would not be mistaken for the number "1". Unicode character U+2114 (℔) is called the "LB Bar Symbol", and it is a cursive development of this symbol. Ultimately, there was the reduction to an overlay of two horizontal strokes (cf. skewed "=") and two forward-slash-like strokes (cf. "//"). Thus, it is misleading to name the symbol "fence" or "square" or representation of the sign with vertical, rather than slanted, strokes.
Other names in English
It has many other names (and uses) in English. (Those in bold are listed as alternative names in the Unicode documentation.)
- comment sign
- fence, gate, grid, gridlet
- hash / hash mark / hash sign
- Hash is most common name for the mark used in the English-speaking world outside North America.
- In Ireland, the UK, Australia, India and New Zealand, "hash key" refers to the # button on touch-tone telephones; "Please press the hash key."
- The symbol is often used as medical shorthand for 'fracture'
- Used among computer professionals. For example, in Unix scripting, it is used in combination with an exclamation mark ("#!") to produce a "shebang" or "hash-bang", used to tell the kernel which program to use to run the script.
- octothorp / octothorpe / octathorp / octatherp
- See for etymology. With some detail at www.octothorp.us
- See Doug Kerr's Octatherp article for detailed alternative etymology of octotherp.
- See Encore magazine article "Pressing matters: touch-tone phones spark debates" for another attribution to Bell engineers, by 1968. Lauren Asplund, who provided the article, says that he and a colleague were the source of octothorp at AT&T engineering in New York in 1964.
- The Merriam-Webster New Book of Word Histories, 1991, has a long article that is consistent with Doug Kerr's essay, in that it says octotherp was the original spelling, and that the word arose in the 1960s among telephone engineers.
- The first appearance of octothorp in a U. S. patent is in a 1973 filing which also refers to the asterisk (*) as a sextile.
- http://www.worldwidewords.org/weirdwords/ww-oct1.htm tells of three possible etymologies, none likely, and says it was not in print until 1974, so the Merriam-Webster story that says it appeared in the 1960s may be more credible.
- Used as the symbol for the pound (the unit of mass) 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 #). It is never called the pound sign in the UK, where that term always denotes the symbol for pounds sterling (£) rather than that for pounds weight (lb).
- 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 clerks' 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"
- resemblance to the glyph used in music notation, U+266F (♯). Since most fonts do not contain the sharp sign, many works use the fallback number sign.
- so called in the name of the Microsoft-invented 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".
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".
- In computing a shebang is the inexact contraction of sharp and bang the typical names of the # and ! signs used at the beginning of executable text files. Also sometimes spoken as "hash-bang," with similar derivation.
- used by editors to indicate where space should be inserted in a proof#noun 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 indicated 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."
Arabic usage of # is the same as in English and is called 'Shoubak' meaning 'window'.
In a telephone keypad it is one of the two standard special keys beyond digits 0 to 9 (the other special key is the star key *). Pressing this # key, a compound tone mixing 941 Hz and 1477 Hz is sent to the line. Its special function depends on services provided by a given telephone-based service.
In a URL the sign is used immediately after the URL of a webpage or other resource to introduce a "fragment identifier" – a
id which defines a position within that resource or a section of the document. For example, in the URL
http://en.wikipedia.org/wiki/Number_sign#Other_uses the portion after the # (
Other_uses) is the fragment identifier (a link such as this will take you to a section in a web page, such as the 'In other languages' section of this article). A relative reference to the fragment from within the document itself can start with the number sign, and consist of just the fragment identifier: TOC refers to an anchor named "top" on the current web page.
In writing press releases, the notation "###" indicates that there is no further copy to come.
In many countries, such as Norway, a "#" is used as a delimiter between different drugs on medical prescriptions.