What is the word for a number sign

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The correct title of this article is #. The replacement of the # is due to technical restrictions.

The symbol # is known variously in English-speaking regions as the number sign,^[1] hash,^[2] or pound sign.^[3] The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔.^[4]

Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as «hashtags»,^[5] and from that, the symbol itself is sometimes called a hashtag.^[6]

The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes.

History[edit]

It is believed that the symbol traces its origins to the symbol ℔,^[a] an abbreviation of the Roman term libra pondo, which translates as «pound weight».^[7][8] This abbreviation was printed with a dedicated ligature type element, 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 slash-like strokes «//».^[8]

The symbol is described as the «number» character in an 1853 treatise on bookkeeping,^[9] and its double meaning is described in a bookkeeping text from 1880.^[10] The instruction manual of the Blickensderfer model 5 typewriter (c. 1896) appears to refer to the symbol as the «number mark».^[11] Some early-20th-century U.S. sources refer to it as the «number sign»,^[12] although this could also refer to the numero sign.^[13] A 1917 manual distinguishes between two uses of the sign: «number (written before a figure)» and «pounds (written after a figure)».^[14] The use of the phrase «pound sign» to refer to this symbol is found from 1932 in U.S. usage.^[15]
The term hash sign is found in South African writings from the late 1960s^[16] and from other non-North-American sources in the 1970s.^{[citation needed]}

The symbol appears to have been used primarily in handwritten material; in the printing business, the numero symbol (№) and barred-lb (℔) are used for «number» and «pounds» respectively.^{[where?][citation needed]}

For mechanical devices, the symbol appeared on the keyboard of the Remington Standard typewriter (c. 1886).^[17] It appeared in many of the early teleprinter codes and from there was copied to ASCII, which made it available on computers and thus caused many more uses to be found for the character. The symbol was introduced on the bottom right button of touch-tone keypads in 1968, but that button was not extensively used until the advent of large scale voicemail (PBX systems, etc.) in the early 1980s.^[18]

One of the uses in computers was to label the following text as having a different interpretation (such as a command or a comment) from the rest of the text. It was adopted for use within internet relay chat (IRC) networks circa 1988 to label groups and topics.^[19] This usage inspired Chris Messina to propose a similar system to be used on Twitter to tag topics of interest on the microblogging network;^[20][21] this became known as a hashtag. Although used initially and most popularly on Twitter, hashtag use has extended to other social media sites.^[22]

Names[edit]

Number sign

‘Number sign’ is the name chosen by the Unicode consortium. Most common in Canada^[23] and the northeastern United States.^{[citation needed]} American telephone equipment companies which serve Canadian callers often 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.^[24]

Pound sign or pound

‘Pound sign’ or ‘pound’ are the most common names used in the United States, where the ‘#’ key on a phone is commonly referred to as the pound key or simply pound. Dialing instructions to an extension such as #77, for example, can be read as «pound seven seven».^[25] This name is rarely used outside the United States, where the term pound sign is understood to mean the currency symbol £.

Hash, hash mark, hashmark

In the United Kingdom,^[26] Australia,^[27] and some other countries,^{[citation needed]} it is generally called a ‘hash’ (probably from ‘hatch’,^[28] referring to cross-hatching, although the exact derivation is disputed).

Programmers also use this term; for instance #! is «hash, bang» or «shebang».

Hashtag

Derived from the previous, the word ‘hashtag’ is often used when reading social media messages aloud, indicating the start of a hashtag. For instance, the text «#foo» is often read out loud as «hashtag foo» (as opposed to «hash foo»). This leads to the common belief that the symbol itself is called hashtag.^[6] Twitter documentation refers to it as «the hashtag symbol».^[29]

Hex

‘Hex’ is commonly used 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.^[30][31]

Octothorp, octothorpe, octathorp, octatherp

Most scholars believe the word was invented by workers at the Bell Telephone Laboratories by 1968,^[32] 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.^[33] 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» digraph, was hard to pronounce in different languages.^[34] The Merriam-Webster New Book of Word Histories, 1991, has a long article that is consistent with Doug Kerr’s essay,^[34] 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^[35] or using the Old English word for village, thorp, because the symbol looks like a village surrounded by eight fields.^[36][37] The word was popularized within and outside Bell Labs.^[38] 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».^[39]

Sharp

Use of the name ‘sharp’ is due to the symbol’s resemblance to ♯, the glyph used in music notation (U+266F ♯ MUSIC SHARP SIGN). The same derivation is seen in the name of the Microsoft programming languages C#, J# and F#. 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’.»^[40] 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».^[41]

Square

On telephones, the International Telecommunication Union specification ITU-T E.161 3.2.2 states: «The symbol may be referred to as the square or the most commonly used equivalent term in other languages.»^[42] Formally, this is not a number sign but rather another character, the Viewdata square ⌗. The real or virtual keypads on almost all modern telephones use the simple # instead, as does their^[whose?] documentation.^{[citation needed]}

Other

Names that may be seen include:^{[43][better source needed]} crosshatch, crunch, fence, flash, garden fence, garden gate, gate, grid, hak, mesh, oof, pig-pen, punch mark, rake, scratch, scratch mark, tic-tac-toe, and unequal.

Usage[edit]

When # prefixes a number, it is read as «number». A «#2 pencil», for example, indicates «a number-two pencil». The abbreviations ‘No.’ and ‘№’ are used commonly and interchangeably.

When # is after a number, it is read as «pound» or «pounds», meaning the unit of weight. The text «5# bag of flour» would mean «five pound bag of flour». The abbreviations «lb.» and «℔» are used commonly and interchangeably. But it is not a replacement for ‘£’.

The latter usage is rare outside North America. The sign is not used to denote pounds as weight (lb or lbs is used for this), and certainly not for pounds currency. The use of # as an abbreviation for «number» is common in informal writing, but use in print is rare.^[44] Where Americans might write «Symphony #5», British and Irish people usually write «Symphony No. 5». British typewriters and keyboards have a £ key where American keyboards have a # key.^[45] Many computer and teleprinter codes (such as BS 4730 (the UK national variant of the ISO/IEC 646 character set) substituted ‘£’ for ‘#’ to make the British versions, thus it was common for the same binary code to display as # on US equipment and £ on British equipment. (‘$’ was not substituted due to obvious problems if an attempt was made to communicate monetary values).

Mathematics[edit]

• In set theory, #S is one possible notation for the cardinality or size of the set S, instead of . That is, for a set , in which all are mutually distinct, This notation is only sometimes used for finite sets, usually in number theory, to avoid confusion with the divisibility symbol, e.g. .
• In topology, A#B is the connected sum of manifolds A and B, or of knots A and B in knot theory.
• In number theory, n# is the primorial of n.
• In constructive mathematics, # denotes an apartness relation.
• In computational complexity theory, #P denotes a complexity class of counting problems. The standard notation for this class uses the number sign symbol, not the sharp sign from music, but it is pronounced «sharp P». More generally, the number sign may be used to denote the class of counting problems associated with any class of search problems.

Computing[edit]

• In Unicode and ASCII, the symbol has a code point as U+0023 # NUMBER SIGN and # in HTML5.^[46]
• In many scripting languages and data file formats, especially ones that originated on Unix, # introduces a comment that goes to the end of the line.^[47] The combination #! at the start of an executable file is a «shebang», «hash-bang» or «pound-bang», used to tell the operating system which program to use to run the script (see magic number). This combination was chosen so it would be a comment in the scripting languages.
  • #! is the symbol of the CrunchBang Linux distribution.
• In the Perl programming language, # is used as a modifier to array syntax to return the index number of the last element in the array, e.g., an array’s last element is at $array[$#array]. The number of elements in the array is $#array + 1, since Perl arrays default to using zero-based indices. If the array has not been defined, the return is also undefined. If the array is defined but has not had any elements assigned to it, e.g., @array = (), then $#array returns −1. See the section on Array functions in the Perl language structure article.
• In both the C and C++ preprocessors, as well as in other syntactically C-like languages, # is used to start a preprocessor directive. Inside macros, after #define, it is used for various purposes; for example, the double pound (hash) sign ## is used for token concatenation.
• In Unix shells, # is placed by convention at the end of a command prompt to denote that the user is working as root.
• # is used in a URL of a web page or other resource to introduce a «fragment identifier» – an id which defines a position within that resource. In HTML, this is known as an anchor link. For example, in the URL https://en.wikipedia.org/wiki/Number_sign#Computing the portion after the # (Computing) is the fragment identifier, in this case denoting that the display should be moved to show the tag marked by <span id="Computing">...</span> in the HTML.^[48]
• Internet Relay Chat: on (IRC) servers, # precedes the name of every channel that is available across an entire IRC network.
• In blogs, # is sometimes used to denote a permalink for that particular weblog entry.
• In lightweight markup languages, such as wikitext, # is often used to introduce numbered list items.
• # is used in the Modula-2 and Oberon programming languages designed by Niklaus Wirth and in the Component Pascal language derived from Oberon to denote the not equal symbol, as a stand-in for the mathematical unequal sign ≠, being more intuitive than <> or !=. For example: IF i # 0 THEN ...
• In Rust, # is used for attributes such as in #[test].
• In OCaml, # is the operator used to call a method.
• In Common Lisp,^[49] # is a dispatching read macro character used to extend the S-expression syntax with short cuts and support for various data types (complex numbers, vectors and more).
• In Scheme, # is the prefix for certain syntax with special meaning.
• In Standard ML, #, when prefixed to a field name, becomes a projection function (function to access the field of a record or tuple); also, # prefixes a string literal to turn it into a character literal.
• In Mathematica syntax, #, when used as a variable, becomes a pure function (a placeholder that is mapped to any variable meeting the conditions).
• In LaTeX, #, when prefixing a number, references an arguments for a user defined command. For instance newcommand{code}[1]{texttt{#1}}.
• In Javadoc,^[50] # is used with the @see tag to introduce or separate a field, constructor, or method member from its containing class.
• In Redcode and some other dialects of assembly language, # is used to denote immediate mode addressing, e.g., LDA #10, which means «load accumulator A with the value 10» in MOS 6502 assembly language.
• in HTML, CSS, SVG, and other computing applications # is used to identify a color specified in hexadecimal format, e.g., #FFAA00. This usage comes from X11 color specifications, which inherited it from early assembler dialects that used # to prefix hexadecimal constants, e.g.: ZX Spectrum Z80 assembly.^[51]
• In Be-Music Script, every command line starts with #. Lines starting with characters other than «#» are treated as comments.
• The use of the hash symbol in a hashtag is a phenomenon conceived by Chris Messina, and popularized by social media network Twitter, as a way to direct conversations and topics amongst users. This has led to an increasingly common tendency to refer to the symbol itself as «hashtag».^[52]
• In programming languages like PL/1 and Assembler used on IBM mainframe systems, as well as JCL (Job Control Language), the # (along with $ and @) are used as additional letters in identifiers, labels and data set names.
• In J, # is the Tally or Count function,^[53] and similarly in Lua, # can be used as a shortcut to get the length of a table, or get the length of a string. Due to the ease of writing «#» over longer function names, this practice has become standard in the Lua community.
• In Dyalog APL, # is a reference to the root namespace while ## is a reference to the current space’s parent namespace.

Other uses[edit]

• Algebraic notation for chess: A hash after a move denotes checkmate.
• American Sign Language transcription: The hash prefixing an all-caps word identifies a lexicalized fingerspelled sign, having some sort of blends or letter drops. All-caps words without the prefix are used for standard English words that are fingerspelled in their entirety.^[54]
• Copy writing and copy editing: Technical writers in press releases often use three number signs, ### directly above the boilerplate or underneath the body copy, indicating to media that there is no further copy to come.^[55]
• Footnote symbols (or endnote symbols): Due to ready availability in many fonts and directly on computer keyboards, «#» and other symbols (such as the caret) have in recent years begun to be occasionally used in catalogues and reports in place of more traditional symbols (esp. dagger, double-dagger, pilcrow).
• Linguistic phonology: # denotes a word boundary. For instance, /d/ → [t] / _# means that /d/ becomes [t] when it is the last segment in a word (i.e. when it appears before a word boundary).
• Linguistic syntax: A hash before an example sentence denotes that the sentence is semantically ill-formed, though grammatically well-formed. For instance, «#The toothbrush is pregnant» is a grammatically correct sentence, but the meaning is odd.^[56]
• Medical prescription drug delimiter: In some countries, such as Norway or Poland, # is used as a delimiter between different drugs on medical prescriptions.
• Medical shorthand: The hash is often used to indicate a bone fracture.^[57] For example, «#NOF» is often used for «fractured neck of femur». In radiotherapy, a full dose of radiation is divided into smaller doses or ‘fractions’. These are given the shorthand # to denote either the number of treatments in a prescription (e.g. 60Gy in 30#), or the fraction number (#9 of 25).
• Press releases: The notation ### denotes «end», i.e. that there is no further copy to come.^[58]
• As a proofreading mark, to indicate that a space should be inserted.^[59]
• Publishing: When submitting a science fiction manuscript for publication, a number sign on a line by itself (indented or centered) indicates a section break in the text.^[60]
• Scrabble: Putting a number sign after a word indicates that the word is found in the British word lists, but not the North American lists.^[61]
• Teletext and DVB subtitles (in the UK and Ireland): The hash symbol, resembling music notation’s sharp sign, is used to mark text that is either sung by a character or heard in background music, e.g. # For he’s a jolly good fellow #

Unicode[edit]

In Unicode, several # characters are assigned. Other attested names in Unicode are: pound sign, hash, crosshatch, octothorpe.

Preview
Unicode name	KEYCAP NUMBER SIGN[72]
Encodings	decimal	hex
Unicode	35 65039 8419	U+0023+FE0F+20E3
UTF-8	35 239 184 143 226 131 163	23 EF B8 8F E2 83 A3
GB 18030	35 132 49 130 53 129 54 184 54	23 84 31 82 35 81 36 B8 36
Numeric character reference	#️⃣	#️⃣
Shift JIS (NTT Docomo)[73]	249 133	F9 85
Shift JIS (SoftBank 3G)[74]	247 176	F7 B0
Shift JIS (au by KDDI)[75]	244 137	F4 89
7-bit JIS (au by KDDI and others)[76]	123 105	7B 69
Emoji shortcode[77]	:hash:

At least three orthographically distinct number signs from other languages are also assigned:

• U+0600 ؀ ARABIC NUMBER SIGN
• U+0BFA ௺ TAMIL NUMBER SIGN
• U+110BD KAITHI NUMBER SIGN

On keyboards[edit]

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 (sterling) sign, £ symbol, and # may be moved to a separate key above the right shift key. If there is no key, the symbol can be produced on Windows with Alt+35, on Mac OS with ⌥ Opt+3, and on Linux with Compose++.

See also[edit]

• sharp sign, ♯
• viewdata square, ⌗,
• equal and parallel to symbol, ⋕
• looped square, ⌘
• the Chinese character for «well» 井
• the game tic-tac-toe

Explanatory notes[edit]

References[edit]

The history of the naming of # is worth a mention.

As the “number sign” or “pound sign” it is first recorded in American English in the OED in 1923

2. U.S. The symbol #, esp. as found on a keyboard or touch-tone telephone; the hash sign.

1923 W. E. Harned Typewriting Stud. ii. 29/1 Special Signs and Characters..#..Number or pound sign; # 10 (No. 10); 10# (ten pounds).

Hash sign does not appear for over more 40 years:

1967 Annual Reports 1960 (Chicago Civil Service Commission) (S. Afr. Council Sci. & Industrial Res.) p. i A slash sign ‘/’ is printed in the line to indicate from which point one should start reading the title, while a hash sign ‘#’ indicates the end of a title.

This leaves us with

octothorp (preferred by OED)

octothorpe (preferred by MW)

octatherp / octotherp (see below)

The OED claims 1973 as the first appearance in print:

1973 U.S. Patent 3,920,926 The pad provides keys for numerals 0 to 9, while..the octothorp (#) key generates a command to send the contents of the memory into the telephone line.

(The patent is assigned to Nortel Networks.)

It suggests as the origin

The term was reportedly coined in the early 1960s by Don Macpherson, an employee of Bell Laboratories:

1996 Telecom Heritage No. 28. 53 His thought process was as follows: There are eight points on the symbol so octo should be part of the name. We need a few more letters or another syllable to make a noun… (Don Macpherson..was active in a group that was trying to get Jim Thorpe’s Olympic medals returned from Sweden). The phrase thorpe would be unique.

However the OED also remarks that another 1996 quote may be the origin:

1996 New Scientist 30 Mar. 54/3 The term ‘octothorp(e)’ (which MWCD10 dates 1971) was invented for ‘#’, allegedly by Bell Labs engineers when touch-tone telephones were introduced in the mid-1960s. ‘Octo-’ means eight, and ‘thorp’ was an Old English word for village: apparently the sign was playfully construed as eight fields surrounding a village.

Merriam Webster states – without reference:

The first known use of octothorpe was in 1971

And adds the origins as

The octo- part almost certainly refers to the eight points on the symbol, but the -thorpe bit is mysterious. One story links it to a telephone company employee who happened to burp while talking about the symbol with coworkers. Another relates it to the athlete Jim Thorpe and the campaign to restore posthumously his Olympic medals, which were taken away after it was discovered that he played baseball professionally previous to the 1912 Games. A third claims it derives from an Old English word for «village.»

However, there is Douglas A Kerr the author of “The names “octatherp” and “octotherp” for the symbol “#”” …

In the early 1960s, Kerr worked for AT&T where he claims that the “octatherp” or “octotherp” was invented or, at least, the “number sign” or “pound sign” was re-christened.

It is an interesting read, and the following is a summary which offers a plausible origin:

At At&T, Lauren Asplund, a member of the data communications marketing group …[wanted] a new, “meaning-neutral”, name for the symbol “#”. He, along with his engineering counterpart, devised the name “octotherp”. He tells me that the inspiration for “octo” was the eight free ends of the four strokes in the symbol. “Therp” did not have any logical premise, but just sounded sort of “Greek-ish”, and thus might confer some scientific stature upon the name.

Shortly after this had happened, John Schaak, an office mate of Asplund’s, called the author to say that the name for the # button would be «octatherp».

Kerr began to circulate it,

For example, when the symbol was mentioned in memoranda or articles I would prepare (for both internal and external use), I would reference a footnote reading, «Often called octatherp.»

Before long, mentions of the name “octatherp” (or, more commonly, “octotherp”) abounded in industry publications. There was a cottage industry of commenters who sought to explain the origin of the name.

Some of these stories were truly “creative”. Several commenters recognized the significance of the “octo” component. One story was that the name was actually “octothorpe” (developed by a different person than as discussed above) and that the latter part was an homage to Olympic great Jim Thorpe.

The story would have ended there but, Ralph Carlsen of Bell Telephone Laboratories wrote an open letter to the editor of the online journal “Telecom Digest” in 1995. Kerr added this version to his paper. In that letter Carlsen wrote that, in 1963, Don MacPherson of Bell Telephone Laboratories was sent to the Mayo Clinic to train staff in telephony and needed a name for the # button and chose the “octo” + “the Olympian “Thorpe”” (hence the “e”).

Kerr, remarks on the now uncertainty of the origins that there was a lot of interchange between Bell, AT&T, and other phone companies.

We may never know the origins.

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