| # | |
|---|---|
Number sign | |
| In Unicode | U+0023 #NUMBER SIGN (#) |
| Related | |
| See also | U+2116 №NUMERO SIGN U+2114 ℔L B BAR SYMBOL |
The symbol# is known as thenumber sign,[1]hash,[2] (in North America) thepound sign,[3] and has a variety of other names. The symbol has historically been used for a wide range of purposes including the designation of anordinal number and as aligatured abbreviation forpounds avoirdupois – having been derived from the now-rare℔.[4]
Since 2007, widespread usage of the symbol to introducemetadata tags onsocial media platforms has led to such tags being known as 'hashtags',[5] and from that, the symbol itself is sometimes incorrectly called ahashtag.[6]
The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes.
It is believed that the symbol traces its origins to the symbol℔,[a] an abbreviation of the Roman termlibra pondo, which translates as "pound weight".[7][8] The abbreviationlb was printed as the dedicatedligature℔, including a horizontal line across (which indicated abbreviation[9]).[8] Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes= across two slash-like strokes//.[8]
In printing, a sign similar to# is used in as a correction symbol in margins to indicate a space is needed between two words, as noted inJoseph Moxon’s 1683 bookMechanik Exercises[10], inPhilip Luckombe’s 1770 book on printing[11] or the 1847 revision ofNoah Webster’sDictionary byChauncey A. Goodrich.[12]
A similar sign (like⌗) has also sometimes been used as a sign for theducat coin,[13][14] other times included with abbreviations starting with D, or as a substitute for themilréis sign.[15] In some 16th century German accounting manuscripts, thenumero sign (№) is written with an N with two extra lines ornamenting it.[16]. The symbol, printed as♯, is described as the "number" character in an 1853 treatise onbookkeeping,[17] and its double meaning (number,pound) is described in a bookkeeping text from 1880.[18] German language references from 1873 or 1892 also shows the symbol for 'ducat' (Ducaten) or 'number' (Nummer), printed as♯[19] or⌗, withnumber also represented with⌗º.[20][b]
The instruction manual of theBlickensderfer model 5 typewriter (c. 1896) appears to refer to the symbol as the "number mark".[21] Some early-20th-century U.S. sources refer to it as the "number sign".[22] A shorthand textbook written in 1903 refers to this symbol as the "pound or number sign" and details its two distinct uses (before and after a number).[23] A 1917 manual distinguishes between two uses of the sign: "number (written before a figure)" and "pounds (written after a figure)".[24] The use of the phrase "pound sign" to refer to this symbol is found from 1932 in U.S. usage.[25]
For mechanical devices, the symbol appeared on the keyboard of theRemington Standard typewriter (c. 1886).[26] It appeared in many of the early teleprinter codes and from there was copied toASCII, 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 oftouch-tone keypads in 1968, but that button was not extensively used until the advent of large-scalevoicemail (PBX systems, etc.) in the early 1980s.[4]
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.[27] This usage inspiredChris Messina to propose a similar system to be used onTwitter to tag topics of interest on the microblogging network;[28][29] this became known as ahashtag. Although used initially and most popularly on Twitter, hashtag use has extended to other social media sites.[30]
Number sign is the name chosen by theUnicode Consortium. Most common in Canada[31] and the northeastern United States.[citation needed] American telephone equipment companies which serve Canadian callers often have an option in their programming to denoteCanadian English, which in turn instructs the system to say "number sign" to callers instead of "pound".[32] This name is rarely used elsewhere in the world, where numbers are normally represented by the lettersNo..
In the United States and Canada, the# key on a phone is commonly referred to as the pound sign,pound key, or simplypound. Dialing instructions to an extension such as#77, for example, can be read as "pound seven seven".[33] This name is rarely used elsewhere, as the termpound sign is understood to meanthe currency symbol £.
In the United Kingdom and Australia,[34][35] it is frequently called ahash (probably fromhatch, referring to cross-hatching[36]). This is also called ahash mark orhashmark.[37]
The termhash sign is found in South African writings from the late 1960s.[38]
Programmers also use this term; for instance#! is "hash, bang" or"shebang".[39]
Derived from the previous, the wordhashtag 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 calledhashtag.[6]Twitter documentation referred to it as "the hashtag symbol".[40]
The termhex 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 termhex is formally discouraged in Singapore in favour ofhash.[citation needed] In Singapore, the symbol is also called "hex" in apartment addresses, where it precedes the floor number.[41][42]
The wordoctothorp[c] was invented by workers at theBell Telephone Laboratories by 1968,[43] who wanted to add an eleventh and a twelfth key to thetelephone keypad and needed named symbols to identify them.[44] While there is typically agreement thatocto- orocta- is here the common prefix meaningeight, various stories abound about the nature of thethorp. Don MacPherson is said to have created the word by combiningocto and the last name ofJim Thorpe, an Olympic medalist.[45] Lauren Asplund declared that he and Howard Eby invented the word in 1964:[46]
We finally decided in a jocular way to call the pound sign an “Octotherp”. That was because it had eight points and “therp” sounded Greek and also seemed to go well with the “octo” portion of the word.
Doug Kerr has written two essays about his recollections on the subject. In the first, in 2006, he wrote:[47]
John C. Schaak and Herbert T. Uthlaut, engineers from two of the Bell Telephone companies [...] had read with interest the part of my report in which I regretted the absence of a unique typographical name for the character "#", and said they had solved my problem by coining one,octatherp. They said that it had no etymological basis, but they had been guided by one principle. They said they were irritated that I had rejected some candidate characters they thought were good on the basis of lack of compatibility with emerging international standards (with which the Bell System had a tradition at the time of little interest). Thus, they said, as a way of getting even, they had included in the name the diphthong [sic] "th", which of course does not appear in German and several other languages and thus might be difficult for users of those languages to pronounce, which would serve them right.
Later, in 2014, after conferring with Asplund, Kerr concluded that the name had likely been invented by Asplund after all:[48]
Lauren Asplund, at the time a member of the data communications marketing group at the AT&T headquarters in New York City, with his AT&T headquarters engineering counterpart (whose name neither of us can recall) [...] 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, and a long time personal friend of mine, called me and said that he had a gift for me. [...] the name "octatherp".
The Merriam-Webster New Book of Word Histories (1991), has a long article (largely consistent with Doug Kerr's later essay) which says "octotherp" was the original spelling, and that the word arose in the 1960s among telephone engineers as a joke. It concludes, after dismissing various other parochial theories:[49]
Howoctotherp was coined is still a mystery, though we are told by a correspondent from the engineering community that it was coined as alark,octo- for 'eight' as previously mentioned, and-therp when somebody burped. Such a tall-sounding tale is not entirely out of the question, given the arbitrariness of some modern scientific coinages.
Other hypotheses for the origin of the word include the last name ofJames Oglethorpe.[50]
The first appearance ofoctothorp in a US patent is in a 1973 filing. This patent also refers to the complementarytelephone star key as "thesextile or asterisk (*) key".[51]
Use of the namesharp is due to the symbol's resemblance toU+266F ♯MUSIC SHARP SIGN. The same derivation is seen in the name of theMicrosoft programming languagesC#,J# andF#. Microsoft says that the nameC# is pronounced 'see sharp'".[52] According to the ECMA-334 C# Language Specification, the name of the language is written "C#" ("LATIN CAPITAL LETTER C (U+0043) followed by theNUMBER SIGN # (U+0023)") and pronounced "C Sharp".[53]
On telephones, theInternational Telecommunication Union specificationITU-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."[54] Formally, this is not a number sign but rather another character,U+2317 ⌗VIEWDATA SQUARE. The real or virtual keypads on almost all modern telephones use the simple# instead, as does most documentation.[citation needed]
When# prefixes a number, it is read as 'number'. "A #2 pencil", for example, indicates "a number-two pencil". This usage is historically rarer in print than the abbreviation 'No.'[55][better source needed], although '#' has recently overtaken 'No.' in total popularity worldwide,[55] stemming from its newfound relatively overwhelming popularity inAmerican English[56] (but notBritish English[57]). In addition to 'No.' and '#', the symbol '№' or just the word 'number' are also used.[58] When used in this manner, # is oftensuperscript, like: "a#2 pencil"[citation needed] — but typically not extending above thecap line.[citation needed]
When⟨#⟩ isafter a number, it is read as 'pound' or 'pounds', meaning the unit of weight.[59][60] The text "5# bag of flour" would mean "five-pound bag of flour". This is rare outside North America.
 | This sectionneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources in this section. Unsourced material may be challenged and removed. Find sources: "Number sign" – news ·newspapers ·books ·scholar ·JSTOR(January 2026) (Learn how and when to remove this message) |
# inHTML5.[61]# introduces a comment that goes to the end of the line.[62] The combination#! at the start of an executable file is ashebang,hash-bang orpound-bang, used to tell the operating system which program to use to run the script (seemagic number). This combination was chosen so it would be a comment in the scripting languages.# at the start of a line starts a preprocessordirective. Inside macros (after#define) it is used for various purposes; for example## is used for tokenconcatenation.# is placed by convention at the end of acommand prompt to denote that the user is working asroot.# is used in aURL of aweb page or other resource to introduce a 'fragment identifier' – an id which defines a position within that resource. In HTML, this is known as ananchor link. For example, in the URLhttps://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<spanid="Computing">...</span> in the HTML.[63]# precedes the name of everychannel that is available across an entire IRC network.# is often used to introduce numbered list items.# is used as a modifier to array syntax to return the index number of the last element in thearray, 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 onArray functions in the Perl language structure article.# is used in theModula-2 andOberon programming languages designed byNiklaus Wirth and in theComponent Pascal language derived from Oberon to denote thenot equal symbol, as a stand-in for the mathematical unequal sign≠, being more intuitive than<> or!=. For example:IFi#0THEN...# is used for attributes such as in#[test].# is the operator used to call a method.# is a dispatchingread macro character used to extend theS-expression syntax with short cuts and support for various data types (complex numbers, vectors and more).# is the prefix for certain syntax with special meaning.#, when prefixed to a field name, becomes a projection function (function to access the field of a record or tuple); also,# prefixes astring literal to turn it into a character literal.#, when used as a variable, becomes a pure function (a placeholder that is mapped to any variable meeting the conditions).#, when prefixing a number, references an arguments for a user defined command. For instance\newcommand{\code}[1]{\texttt{#1}}.# is used with the@see tag to introduce or separate a field, constructor, or method member from its containing class.# is used to denote immediate mode addressing, e.g.,LDA #10, which means "load accumulator A with the value 10" inMOS 6502 assembly language.# is used to identify a color specified inhexadecimal format, e.g.,#FFAA00. This usage comes fromX11 color specifications, which inherited it from early assembler dialects that used# to prefix hexadecimal constants, e.g.: ZX SpectrumZ80 assembly.[66]#. Lines starting with characters other than# are treated as comments.# (along with$ and@) are used as additional letters in identifiers, labels and data set names.# is theTally orCount function,[68] and similarly inLua,# 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.# is a reference to the rootnamespace while## is a reference to the current space's parent namespace.# character is used in based integer literals, which take the formbase#digits#, wherebase is an integer from 2 to 16 specifying the radix, anddigits are the digits valid in that base (0-9, optionally A-F for bases above 10). | This sectionneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources in this section. Unsourced material may be challenged and removed. Find sources: "Number sign" – news ·newspapers ·books ·scholar ·JSTOR(January 2026) (Learn how and when to remove this message) |
# and other symbols (such as thecaret (^)) have in recent years begun to be occasionally used in catalogues and reports in place of more traditional symbols (esp.dagger, double-dagger,pilcrow)./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).#NOF is often used for "fracturedneck 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).The number sign was assigned code 35 (hex 0x23) in ASCII where it was inherited by many character sets. InEBCDIC it is often at 0x7B or 0xEC.
Unicode characters with 'number sign' in their names:
Additionally, a Unicode named sequenceKEYCAP NUMBER SIGN is defined for thegrapheme clusterU+0023+FE0F+20E3 (#️⃣).[78][d]
On the standardUS keyboard layout, the# symbol is⇧ Shift+3. On standard UK and some other European keyboards, the same keystrokes produce thepound (sterling) sign,£ symbol, and# may be moved to a separate key above the right shift key.
The Italianlibbra (from the old Latin wordlibra, 'balance') represented a weight almost exactly equal to theavoirdupois pound of England. The Italian abbreviation oflb 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.'
#—Preceding a figure (thus, # 10) means number.
#—After a figure (thus, 10 #) means pound.
It is best to use the 'number mark' for plus; the hyphen for minus, and two hyphens for the sign =
Recently there were sent by mail to the Kansas banks engraved reproductions of a draft issued by an Ohio bank on its New York correspondent for ten dollars which had been raised to ten thousand dollars and successfully negotiated in Buffalo, New York. It was sent out as a means of advertising a check protecting machine but it will serve us for illustration. I presume many of you, and perhaps all of you, have seen it. The number sign used immediately following the word ten in the body of the draft and part of the line drawn along the unoccupied space from it to the word dollars in the right hand margin had been removed with acid and the word thousand written in. The number sign following the memorandum figures $10 in the end margin had likewise been removed and three ciphers added. The number sign had then been added after both the added word and the added ciphers, so that the draft in its altered form read Ten Thousand#———— Dollars in words in the body and $10000# in figures in the margin with the only significant peculiarity in the make-up of the draft, the number sign following both the written words in the body and the memorandum figures in the margin, relatively in the same position as in the draft as originally issued.
Make the (#) pound or number sign thus: 37⁺ = 37 lbs. ⁺37 = No. 37.
APPENDIX I. SIGNS AND SYMBOLS. [...] #. . . . . . .number (written before a figure). [...] #. . . . . . .pounds (written after a figure).
Number or Pound Sign (#) 1. Before figure fornumber. #16. 2. After figure forpound.
In Australia, however, it was better known as the 'hash' sign and only used to mean 'number'.