# What is this symbol? **URL:** \ **Category:** Factual Questions\ **Created:** [August 18, 2003, 6:10pm UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008 "2003-08-18T18:10:59Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [August 19, 2003, 12:52am UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/21 "2003-08-19T00:52:32Z")
Yeah, well if you search the web for “E𝄬 major” I bet you’ll get a lot fewer hits than with “Eb major”. That doesn’t mean that “b” is the correct way to write “flat” and “𝄬” is incorrect, but you use “b” when it’s more convenient. (𝄬 is apparently the Unicode character for the musical flat sign - my browser doesn’t show it.) ---
**Author:** ![moriah](https://avatars.discourse-cdn.com/v4/letter/m/b2d939/32.png) [@moriah](https://boards.straightdope.com/u/moriah)\ **Post date:** [August 19, 2003, 2:15am UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/22 "2003-08-19T02:15:08Z")
> [@](#): > > \*Originally posted by Phlosphr \* > \*\*It denotes a zero. So you do not get it confused with an “O” usually when hand writing something. I do not know it’s proper name aside from ZERO. \*\* About 8 fonts on my computer us it for zero. ## Peace. It’s ‘O’ in Leetspeak. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [August 19, 2003, 3:18am UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/23 "2003-08-19T03:18:05Z")
Ø also is used to express dimensional diameters, like in measuring a tube, for example: 2cm inner Ø, 2.5cm outer Ø. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [August 19, 2003, 3:23am UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/24 "2003-08-19T03:23:30Z")
Ø also is used to express dimensional diameters, like in measuring a tube, for example: 2cm inner Ø, 2.5cm outer Ø. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [August 19, 2003, 3:30am UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/25 "2003-08-19T03:30:32Z")
Oops… I think my clone get out of the cage again… 😛 ---
**Author:** ![cybersnark](https://avatars.discourse-cdn.com/v4/letter/c/b9e5f3/32.png) [@cybersnark](https://boards.straightdope.com/u/cybersnark)\ **Post date:** [August 21, 2003, 6:23pm UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/26 "2003-08-21T18:23:32Z")
> [@](#): > > \*Originally posted by Gary T \* > \*\*No. > > Correct. > > Phi has a **vertical** line. \*\* Sorry, I am correct here. The UPPER CASE Phi has a vertical line, the lower case Phi does not, but has a slash as shown in tomndebb’s post. Regarding the use of this symbol to represent a diameter of a pipe or tube, I’ve only seen it used to measure outer diameter, with the idea that the symbol is kind of a overwriting of an “O” and a “D”. However, that is merely my anecdotal experience, ad I do not know if it is truly universal. ---
**Author:** ![DogMom](https://avatars.discourse-cdn.com/v4/letter/d/e9c0ed/32.png) [@DogMom](https://boards.straightdope.com/u/DogMom)\ **Post date:** [August 21, 2003, 8:13pm UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/27 "2003-08-21T20:13:23Z")
It actually can represent any diameter - OD, ID, holes, etc. It’s also used in Geometric Dimensioning and Tolerancing to indicate a circular feature OR to indicate the tolerance is diametrical if it’s used in a feature control frame. [http://www.engineersedge.com/gdt.htm](http://www.engineersedge.com/gdt.htm) ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [August 21, 2003, 9:49pm UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/28 "2003-08-21T21:49:58Z")
> [@](#): > > \*Originally posted by cybersnark \* > Sorry, I am correct here. The UPPER CASE Phi has a vertical line, the lower case Phi does not, but has a slash as shown in tomndebb’s post. Sorry, you are incorrect and all you have to do is look at a font chart. Look at the symbol font and you will see the entire greek alphabet, upper and lower case and they are totally different and distinct from the null sign being discussed. The letter o and the number 0 look alike but have different ascii symbols and are not the same thing. The null symbol and the lower case phi do not look alike at all and have different symbols. in fact there are TWO lower case phi in the symbol font (corresponding to f and j) and they both look totally different from the null sign. So, sorry, you are mistaken. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [August 21, 2003, 9:59pm UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/29 "2003-08-21T21:59:31Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > It may be, as you say, the wrong symbol, but it’s a popular wrong symbol–more so even than the “correct” one. I’d even go so far as to say at this point Ø _is_ the correct symbol by default, purism be damned. I believe the reason that it is used is that it is part of the basic Latin-1 (ISO 8859-1) Character Set set (#216, Capital O with oblique stroke) whereas you have to change to the symbol font to do the Greek letters which may be messy or impossible depending on what you are doing, but people are still calling it phi (phi = phase, get it?) ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [August 21, 2003, 10:08pm UTC](https://boards.straightdope.com/t/what-is-this-symbol/196008/30 "2003-08-21T22:08:11Z")
A table with the Latin-1 (ISO 8859-1) Character Set (used by browsers) can be found at [http://www.pemberley.com/janeinfo/latin1tb.html](http://www.pemberley.com/janeinfo/latin1tb.html) and, as you can see, the greek letters are not in there but the O-slash is. [Previous page](https://boards.straightdope.com/t/what-is-this-symbol/196008.md?page=1)