When using an abbreviation or acronym that has a mix of lowercase and capital letters, such as mmWave or dBm, in a heading or line that is formatted in all caps, is it appropriate to use all caps - or should you leave the mixed caps?

  • 1n what medium? If online, what software are you using? What style guide are you following, that mandates capitals? I suggest using caps and small caps. Provided that you have small caps available and may use them.
    – Rosie F
    Feb 21, 2021 at 8:30
  • 3
    dB·m is a symbol, not an abbreviation, and in that distinction lies your answer. (Dot or space symbol strings. NIST 811
    – Phil Sweet
    Feb 21, 2021 at 12:53
  • See also NIST 811 7.8, which would likely apply to headings.
    – Phil Sweet
    Feb 21, 2021 at 12:58
  • I agree with the answers regarding symbols for SI units and such, but with stylised mixed-case or lower-case brand names, band names, etc, it's different, and common to put them into another, more normal form. (See e.g. this discussion)
    – Stuart F
    Nov 18, 2021 at 23:28

2 Answers 2


I would tend to use mixed cases especially if the abbreviation or acronym had a special meaning. Decibel is written as dBa. Reading that I immediately know you are speaking of sound however changing the case can often distort or confuse the reader.


is it appropriate to use all caps - or should you leave the mixed caps?

Leave the mixed capitals!

From the IEEE website APPENDIX VII Recommended Unit Symbols, SI Prefixes, and Abbreviations:

M = mega, e.g. 20MW = twenty million Watts,


m = milli e.g. 20mW = twenty milliwatts = 0.02 Watts

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