My PI helps to modify my thesis. He keeps changing the degree mark '°' to '0' as the superscript in a degree centigrade mark. He also changes every 'in the phase' to 'at the phase'.

As I searched, superscript 0 was used when initially creating the degree mark. But now ° is used in all the degree mark. 'Phase' means a period of time and in most paper and textbooks, people use 'in the phase'.

I'm confused about these changes. Is the '°' wrong, or 'in the phase' wrong? What do you use in the paper/thesis writing?

An example of using '°' and 'phase' in my thesis: 'The cells cultured at 30 °C for 3 days were in the stationary phase.' 'Stationary phase' is one of the cell-growth phases that range from several hours to several days.

Thanks to @Houska for your vision and practical suggestions <3

Thanks to @AndreasRejbrand for correcting the degree sign to be 'U+00B0: DEGREE SIGN'. I have changed the sign in the title and body. In my PI's comments, he highlighted my degree sign (that I added through 'Symbols' in MS Word) and commented 'Should be a zero in superscript! Change all the rest.' So I believe he means using a zero.

PS. My PI is a Chinese who has been working in the UK for 20 years. His spoken English is fine, but sometimes he mixes up "she" and "he", or forgets to add 's' in a verb with the third person.

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    @Aruralreader - 23 Coulombs is very different from 23 degrees Celsius - you must use the degree symbol. My AIP style manual (American Institute of Physics) clearly indicates that the degree symbol is not a superscripted zero but instead its own thing.
    – Jon Custer
    Commented Apr 8, 2021 at 17:00
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    @Aruralreader and AppliedAcademic: given that the question refers to "phase", it has probably nothing to do with degree Celsius ;-) Commented Apr 8, 2021 at 17:05
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    @MassimoOrtolano - fair enought, but that style manual is also quite clear that the degree symbol (whether degrees Celsius or not) is the degree symbol, not a superscripted zero.
    – Jon Custer
    Commented Apr 8, 2021 at 17:12
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    Can you give an example sentence where you use "at the phase" or "in the phase"? Possibly either could be grammatical depending on the context. Commented Apr 8, 2021 at 17:35
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    I wonder if you are sending an electronic document back and forth and the professor's machine is either doing "autocorrecting" or is missing the fonts you are using and does a substitution.
    – Buffy
    Commented Apr 8, 2021 at 18:13

4 Answers 4


For the International System of Units, the units of measurements are defined by the SI brochure. For the degree, unit of plane angle, and the degree Celsius, unit of Celsius temperature, the SI brochure at p. 133 and at p. 149 uses a circle and not a zero.

However, at table 8, the circle is rendered with an "o" (probably they didn't have the circle in that font). In any case, no zero.

You can refer your professor to that document. Further, if you're using LaTeX, you can use the siunitx package and write the angles with the command \ang and Celsius temperatures with the command \SI{23}{\celsius} (example with 23 °C). From the package documentation, you can see that also in this case the degree symbol is a circle.

If they still insist, let it go.

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    Also, if you are using LaTeX you might want to set up a macro so that by editing one line at the start of your document you can change every instance to a superscript 0 (to please your PI) or the proper degrees sign (to conform to the SI standard).
    – dbmag9
    Commented Apr 9, 2021 at 10:29
  • @dbmag9 If you use siunitx there’s no need to set up a macro because the symbol is customisable through an option ;-) Commented Apr 9, 2021 at 10:33
  • I'm considering switching to LaTeX. My PI only uses MS Word so I still need to change the file type before sending it to him :(
    – Metis533
    Commented Apr 9, 2021 at 14:58
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    @Metis533 If you don't know it yet, a free tool that could help with the conversion is pandoc. For complex documents the conversion is not perfect, but it's a starting point. Commented Apr 9, 2021 at 15:05
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    @Metis533: Given that your PI is using MS word, I am suspicious that the real reason your PI is correcting you is that his machine is failing to render the degree symbol properly. Then, he thinks he is sending an e-mail like: "Stop using ◘ as your degree symbol!" but your machine renders his e-mail as, "Stop using ° as your degree symbol!" This would make for a confusing e-mail exchange. If this is the issue, you may need to embed your fonts into the MS word document. Possibly Andreas's recommendation to use ° would fix this.
    – Brian
    Commented Apr 9, 2021 at 16:33

As you (presumably) continue down the academic career path, you will be buffeted by all sorts of "helpful suggestions" that span the range from ignorable noise to microbullying by those in positions of authority over you. Editors wanting picky little formatting edits, some good some bad. Reviewers with weird comments. Granting agencies and university bureaucrats wanting you to fit something to their format or structure even though it makes no sense in the context.

Choose your battles. Let people "win" on the small stuff if it greases the wheels to get the real help and support you need.

Fighting over degree symbols is pretty certain to not be a battle worth fighting. If your P.I., your University thesis office, or a journal publisher wants it some specific way, just do it. And be prepared to revert back if someone else with higher positional authority wants it differently (e.g. the publisher of your accepted paper trumps your PI).

As to your "phase" question, I'm a bit confused about it. But apply the same logic. Maybe it's sufficiently wrong or jarring to insist on doing it right, maybe it's not worth the bother. And maybe you can just smilingly say, "no, I'm sure this is right. If you want, I'll double check."

Finally, recognize that someone's pencilled edits on a manuscript may not mean "I insist on this other way" but "I'd do it this way, use your judgment". So maybe you can just say, "thank you for the comments" and not do it.

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    Picky edit to end of 1st paragraph: you probably mean "even though it makes no sense". Commented Apr 9, 2021 at 16:23
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    @DanielR.Collins or it could mean "even though it already makes sense" (without making the requested change). Commented Apr 9, 2021 at 16:49
  • Upvoted, even though I'd be incapable of taking your advice in this case!
    – jpaugh
    Commented Apr 9, 2021 at 20:10

Yes, it is completely wrong to use ˚ as a degree sign.

The reason is that ˚ is U+02DA: RING ABOVE. It is not at all a degree sign; instead, it is (semantically) the ring above the A in Å.

The correct character is °, U+00B0: DEGREE SIGN.

This is almost the first time I have seen someone misuse U+02DA: RING ABOVE as the degree sign.

However, it is very common that people misuse the masculine ordinal indicator, º, U+00BA: MASCULINE ORDINAL INDICATOR as a degree sign, especially in fonts in which it is not underlined. The ordinal indicator is used in some languages to indicate ordinal numbers, e.g. for primo in Italian.

  • Note: Just &deg; in HTML (including StackExchange questions and answers, but not comments).
    – Nat
    Commented Apr 9, 2021 at 12:52
  • Good catch, it would not occur to me that the symbol might be some other ˚ when ° is what I can find on my keyboard. I guess Scandiavian keyboard users might have it the other way. Commented Apr 9, 2021 at 14:37
  • There's also U+2070: ⁰, which is explicitly the "Superscript Zero". Not sure if this is what the OP is referring to? Commented Apr 9, 2021 at 18:32
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    For those confused: the original question was using the RING ABOVE character in the title and has since been edited to the degree sign. Even with the current edit it's useful to see additional incorrect ways this sign might show up. Commented Apr 9, 2021 at 18:51

There's a single Unicode character "℃" which could save you having to think about all this.

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    I would advise against doing this, most latin fonts don't render this character correctly. According to the wiki, citing the Unicode standard, it is recommended to use °C instead of ℃ (unless you're writing in East Asian scripts, where using the single character will likely typeset better, as a single full-width character). Commented Apr 9, 2021 at 9:23
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    Good find, @RichardtheSpacecat. I can confirm that the Unicode standard really says what the Wikipedia article cites it as saying. Why not rewrite your comment as an answer? Commented Apr 9, 2021 at 9:35

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