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I used to say "sharp sign" to refer to the # sign.

Today a friend told me that the correct term is number sign or hash sign or even just hash.

What is the difference between these options and what's the correct usage of the names for this sign?

waiwai933
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  • Computer geeks (and increasingly now, Anglophones in general) call it "hash". Musicians call it "sharp". It's a bit irrelevant whether they follow that designation with the additional clarification "sign". – FumbleFingers Apr 04 '14 at 20:11
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    @FumbleFingers the sign by itself doesn't have a name if it's out of any context? ("Look a cloud shaped like a 'insert-correct-name' sign in the sky!") – Michel Ayres Apr 04 '14 at 20:15
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    The musical sharp (♯) is technically a different character from the octothorpe (#), though they are superficially similar. The Wikipedia article describes the origin of the alternative names number sign, pound sign, and hash among others. – choster Apr 04 '14 at 20:15
  • @Michel: There's no recognised authority bestowing "official" names on such simple symbols, most of which are used in a variety of contexts with different meanings. Bizarrely, increasing numbers of Americans call # the "pound sign", but to Brits it has no connection whatsoever to our actual symbol £. – FumbleFingers Apr 04 '14 at 20:22
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    @FumbleFingers It’s a pound sign because of weight, not currency. Comes from grocery store practices and such. In the world of programming, in C you have pound defines and pound includes. – tchrist Apr 04 '14 at 20:24
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    @tchrist: Maybe you do, but as a Brit I've only ever heard and used *hash defines* and *hash includes*. – FumbleFingers Apr 04 '14 at 20:30
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    @FumbleFingers We no more use # to represent sterling than we use £ to represent weight. We consider those two separate things; perhaps you do not. – tchrist Apr 04 '14 at 23:15
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    Related: http://english.stackexchange.com/q/117219 http://english.stackexchange.com/q/27333. Please note that octothorp was a Bell Labs innovation, and that nobody actually calls it that. Unicode calls it a NUMBER SIGN and notes that it has also been called a “pound sign, hash, crosshatch, octothorpe” in the past, and that it is distinct from a MUSIC SHARP SIGN. – tchrist Apr 04 '14 at 23:49
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    @FumbleFingers - that's hard to believe! It was used as pound since the middle ages, the history of which is written in English, and includes England prominently. As to it's relation to £, see below please. – anongoodnurse Apr 04 '14 at 23:49
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    Calling Microsoft and other automated systems in my line of work, I will often hear it referred to as the hash key, pound key and sometimes even just the square. However, I am a UK resident and, like FF, I mostly hear it referred to as a 'hash'. But I've never seen it used for notation of weight. As for 'sharp', it's distinct from the musical sharp because the sharp symbol slants upwards rather than to the right. (edit: just noticed Choster beat me to the punch there by three hours. sorry.) – NinjaDuckie Apr 05 '14 at 00:06
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    @tchrist The fact that it's used for lbs not £s is neither here nor there. As FumbleFingers pointed out, we already have a heavily used sign called the "pound sign" so ascribing the name "pound sign" to a symbol that is not commonly called that when we have one that is would create utter confusion. – starsplusplus Apr 16 '14 at 17:12
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    https://separatedbyacommonlanguage.blogspot.com/2010/07/hash-sign-and-pound-sign.html#:~:text=It%20is%20also%20called%20the,often%20used%20in%20that%20way. Also, bear in mind that # and @ appeared in American receipts or orders well before the existence of computers. – Lambie Jan 08 '22 at 20:52

6 Answers6

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In What Is the Real Name of the #?, a good explanation of this sign is given. Technically, it's called the octothorpe.

Called the pound sign, number sign and more recently the hashtag, it actually developed as a scribble for the abbreviation of pound in latin: lb, where lb is an abbreviation of libra, itself a shortened form of the full expression, libra pondo - literally “pound by weight” in Latin (though the Roman pound was only 12 ounces, not 16.)

Libra for a pound is first found in English in the late fourteenth century, almost at the same time as lb started to be used.*

If you look at how scribes scribbled lb, you might recognize the sign (in the first example) amongst the scribbled and attached lines. The reason they continued the 'b' to make it into a cross stroke was to indicate that letters were left out (i.e. it was an abbreviation.) The more careful rendition also has the cross stroke indicating abbreviation.

enter image description here

That is still how it's scribbled: I do it myself when recording the weights of babies in pounds and ounces (though we are finally moving to kilograms).

The phrase “number sign” arose in Britain because “pound sign” could easily be confused with the British currency. The # symbol is sometimes spoken as the word “number” ("number two pencil"). Another abbreviation for libra pondo became the standard symbol for the British pound in the monetary sense. Written "£", it is an ornate form of L with a cross-stroke, the way medieval scribes marked an abbreviation (from which, incidentally, we get our apostrophe). The link between pound weight and money is that in England a thousand years ago a pound in money was equivalent to the value of a pound of silver.

It appears on telephones. The name octothorp was coined by someone working for a phone company. It refers to it's eight (octo) points + thorpe (derivation questionable and possibly a joke by the person who coined it.)

Hash tag (the twitter name is twittertag) comes from its use (along with the ampersand) in IT as a tag to group information. The term twitter tag was coined by Chris Messina and popularized in a column by Stowe Boyd.

It is sometimes called the octothorn, an alternate (mis)pronunciation of octothorpe.

Sometimes it is called the tic-tac-toe sign because of the vertical and horizontal lines drawn in a game of tic-tac-toe are similar pattern to that used in #.

The sharp is slightly different in that the vertical lines are straight up-down and the cross strokes are inclined. calling # a sharp is a misnomer for the pound, or number sign.

But from the 1300s, it has been known as the pound sign, or, in England, the number sign.

herisson
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anongoodnurse
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    Except that a pound of silver weighs 12 troy ounces, so ~373 grams, while a pound of artichokes weighs 16 avoirdupois ounces, so ~454 grams. That’s why a pound of feathers outweighs a pound of gold in the old riddle. But I do fully agree that the # scribal abbreviation derives from libra, howsoever many ounces and of what ilk that pound should contain. – tchrist Apr 04 '14 at 23:32
  • @tchrist - thank you for that! Added interest tothe question, and the answer for a joke. Who could ask for more? – anongoodnurse Apr 04 '14 at 23:33
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    The pound we use to measure precious metals in has just 12 ounces not 16, just like the Roman’s version. – tchrist Apr 04 '14 at 23:35
  • @tchrist - excellent. see above. :) – anongoodnurse Apr 04 '14 at 23:35
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    There’s also the whole set of apothecary measures, whence some of this derives. That’s why a troy ounce is exactly 480 grains and a troy pound 5,760 grains, while an avoirdupois ounce has 437½ grains and a pound avoirdupois exactly 7,000 grains. It should also be noted somewhere that despite all this octothorp silliness, the official Unicode name for the # character at U+0023 is NUMBER SIGN. – tchrist Apr 04 '14 at 23:43
  • @tchrist - gosh, that's some good (and not well known, I believe) information. I feel like posting a question about pound... though it would soon be shut down as OT. :( – anongoodnurse Apr 04 '14 at 23:47
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    medica and @tchrist, there is also this question that deals with the pound issue itself (though from a different perspective). Some of the comments in particular make my non-mathemagical mind writhe and boggle. – Janus Bahs Jacquet Apr 06 '14 at 12:34
  • @JanusBahsJacquet - very cool thread + great answer. Thanks for pointing me to it. :) (and how many languages do you know‽‽) (that's the first double interrobang I've ever used) – anongoodnurse Apr 06 '14 at 12:54
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    This answer is missing the name "hash" or "hash mark". ("Hashtag" is a red herring: it was named for the hash mark, not the other way around.) – Marthaª Apr 09 '14 at 20:21
  • @medica: I can find no evidence on the internet for this sign being used for "pound" (or anything else, for that matter) before the last years of the 19th century. (I don't count that scribble as a pound sign; it's looks more like an lb.) Do you actually have any hard evidence it was used prior to that? – Peter Shor Apr 11 '14 at 21:16
  • Absolutely. And it is an lb. As I stated, If you look at how scribes scribbled lb... – anongoodnurse Apr 11 '14 at 21:29
  • I guess my question is: when and where was the lower loop on the *b* dropped? And also when did it start meaning "number" as well as "pounds". – Peter Shor Apr 11 '14 at 21:43
  • @PeterShor - :D If you want 250 points, that's exactly the kind of information I offered the bounty for! – anongoodnurse Apr 11 '14 at 22:13
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    I've tried looking … didn't get anywhere, although I suspect the timeline may be that the # sign replaced the lb sign on early typewriters. I would be surprised if it was a common handwritten abbreviation in the U.S. before that. – Peter Shor Apr 11 '14 at 23:54
  • Oops. I meant "wouldn't be surprised" in my last comment. – Peter Shor Apr 13 '14 at 14:14
  • I heard it called a "hash key" (on phones etc.) long before Twitter popularised it :) – starsplusplus Apr 16 '14 at 17:15
  • @medica, http://www.worldwidewords.org/weirdwords/ww-oct1.htm "With all these terms about, inventing a new one, especially such an odd-ball one as octothorpe, would seem to serve no practical purpose" – Pacerier Feb 28 '15 at 12:35
  • You should have given the bounty to yourself. This answer is without the cultural bias of the other, has better chronological order, and contains the origin of the symbol. – Mazura Jul 07 '17 at 10:25
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    Typographer, poet and book designer Robert Bringhurst, in his book, The Elements of Typographic Style, writes that, in cartography, the octothorp "is a traditional symbol for village: eight fields around a central square. That is the source of its name. Octothorp means eight fields." I'm not sure he's correct, since "thorp" means village, but it's an interesting theory anyway. – jdscomms Jan 08 '22 at 21:53
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Hashtag
Wikipedia

The use of the hash symbol in IRC inspired Chris Messina to propose a similar system to be used on Twitter to tag topics of interest on the microblogging network. He posted the first hashtag on Twitter:

“how do you feel about using # (pound) for groups. As in #barcamp [msg]?" —Chris Messina, ("factoryjoe"), August 23, 2007

enter image description here

The first use of the term "hash tag" was in a blog post by Stowe Boyd, "Hash Tags = Twitter Groupings," on 26 August 2007, according to lexicographer Ben Zimmer, chair of the American Dialect Society's New Words Committee.

Beginning July 2, 2009,Twitter began to hyperlink all hashtags in tweets to Twitter search results for the hashtagged word (and for the standard spelling of commonly misspelled words). In 2010, Twitter introduced "Trending Topics" on the Twitter front page, displaying hashtags that are rapidly becoming popular.

According to an article in The Guardian, the term octothorpe was invented by engineers at Bell Laboratories in the early 1960s. They wanted a name for one of two non-number function symbols on the first touch-tone keypads (the other was the *, which they called a sextile). The term was practically unheard of among the general public until Twitter arrived.

Oxford Dictionaries claim hash has its origin in the 1980s: probably from the verb sense of hatch, altered by folk etymology, meaning 'to cut, engrave, or draw a series of lines'.

The earliest recorded usage of the octothorpe symbol as an abbreviation or shorthand for pound, as in weight, is dated 1923 by the OED:

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

On a survey on keypad terminology conducted by the University of Edinburgh it was noted that the most common names for Keys to the Right of Zero were: square, hash and gate

enter image description here

Other names for the octothorpe

  • number sign (USA)
  • pound sign/symbol (USA)
  • tick-tack-toe sign/tictactoe
  • the crosshatch symbol
  • the double-cross symbol
  • hash mark/sign (UK)
  • gate (UK, and in Italian it is called cancelletto)
  • square (UK)
  • crunch
  • a symbol for fracture
  • space (in proofreading "#" indicates "insert space here")
Laurel
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Mari-Lou A
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  • I'm glad you took this question on. It's good to know where/when hash was first used, and your chart is very interesting. Your answer seems to support Peter Shor's comment. Thanks, Mari-Lou. – anongoodnurse Apr 13 '14 at 02:44
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    @medica This was a rushed, botched and basically a copy'n'paste job. Your post is the best of the bunch, I was just a little amazed that nobody had really attempted to answer after a week. I made the post a community wiki one, thinking the bounty (if it was awarded to me) would go somewhere in outer-wiki-space. It hasn't. – Mari-Lou A Apr 13 '14 at 06:36
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    Enjoy the bounty. You deserve it. I'm glad you answered the question. ') – anongoodnurse Apr 13 '14 at 09:19
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    I'm changing the acceptable answer to yours @Mari-LouA, @Medica made an amazing answer too, but your have some amazing facts about the historic value of the sign itself. Thank you both. – Michel Ayres Apr 13 '14 at 15:49
  • I never heard it called a hash until Twitter. It was always either "pound sign" (popular with phonemail systems) or "number sign". And, of course, the amusing "official" name was "octothorpe". (The chart above is clearly not representative of US usage since it omits both "pound sign" and "number sign".) – Hot Licks Mar 05 '15 at 19:35
  • And I should add that one term I heard used by computer geeks in the early 70s was "pig pen". – Hot Licks Mar 05 '15 at 19:37
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    Excellent post. Although I think it can be improved by changing the first line that says "Hashtag" to just "Hash". After all, the symbol isn't called a hashtag; the symbol + tag-word attached is the hashtag. The symbol is just plain called a hash. Having it worded like that implies the symbol is called a hashtag. – SarahofGaia Sep 21 '15 at 19:30
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    @SarahofGaia the linked Wikipedia article is called hashtag, and the image posted below is titled hashtag, I then list its other names, for some it is a hatch, an octothorpe or even "number sign". – Mari-Lou A Sep 21 '15 at 19:42
  • @Mari-LouA: Oh, so that's the name of the article? I didn't know that. Looks like you said that as your answer, and then below that you gave more detail as to why. – SarahofGaia Sep 21 '15 at 20:47
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    @SarahofGaia you might have a point there, it seem like that to me at the time. I'll edit it. Thanks for mentioning it. – Mari-Lou A Sep 21 '15 at 20:50
  • Hey no problem. Glad to help. :) – SarahofGaia Sep 23 '15 at 19:48
  • Funny that the inventor of the hashtag calls the symbol (pound) in his proposal for hashtags... – shoover Jan 09 '22 at 04:42
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The sign has multiple names and meanings:

Per Wikipedia:

The symbol is a Number Sign in North America with Pound Sign making in-roads as a name.

Outside North America it has always been called a Hash Sign.

With the advent of Twitter, hash or hashtag (named for the act of tagging with a hash sign) has become very popular in North America, too.

The Sharp Symbol in music is extremely similar, but usually looks like a hand-written version.

David M
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  • Following your answer, a phrase without context would be like: "Look! A cloud shaped like a hash in the sky!" ? – Michel Ayres Apr 04 '14 at 20:21
  • @Michel Yes. Although you'd likely say hash sign. – David M Apr 04 '14 at 20:31
  • @MichelAyres At least where I live it would not be at all odd to say that (other than the fact I dont think many clouds look like # :P). That shape is generally just called a hash in much of the UK, particularly in computing and engineering communities but also in the general population. – Vality Apr 11 '14 at 22:36
  • @MichelAyres With a little context, it could be just hash. e.g. "hash define" (#define), "star hash one hundred hash" (*#100#), "To go to the main menu, press hash." etc. However if it really was something as abstract as a cloud shape, "hash symbol" or "hash sign" would be more likely. – starsplusplus Apr 16 '14 at 17:19
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Octothorpe/Octothorp

Not to be confused with the Chinese character 井 (well), the sharp sign (♯), the viewdata square (⌗), or the numero sign (№)
Number sign is a name for the symbol #, which is used for a variety of purposes, including the designation of a number (for example, "#1" stands for "number one").

Mari-Lou A
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Third News
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1

As others have said the number sign is technically called on octothorpe. Not that anyone would know what you were talking about if you used it. Number sign, pound sign, or hash/hashtag would be more generally understood. Almost all automated phone systems will use the term 'pound' if they want you to press it on your phone.

"Sharp" is a completely different symbol to the octothorpe. Using the term "sharp" is related to music and musical notation. The terms are not interchangeable, as they look different from each other. "Sharp" looks kind of like a number sign in backwards Italics.

Compare the octothorpe (number/pound sign): #

to the sharp sign: ♯

Two different symbols.

Shane
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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.

Greybeard
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