Re: SI prefixes with "accepted" units, others

Joseph,

Thanks for the reference.  This led me to the more or less the definitive
statement I was looking for.

On the bipm.org site, I found this "brochure"
<https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507?version=3.0&t=1725283751897&download=true>
which says:

> Prefixes may be used with any of the 29 SI units with special names with
> the exception of the base unit kilogram, which is further explained in
> chapter 3.


I haven't double checked, but I believe these are 7 base units and the 22
derived units.

For the accepted units it says:

> The SI prefixes can be used with several of these units, but not, for
> example, with the non-SI units of time.


That's a little less definitive but does rule out "khr", etc.

Also, going through the document, I spotted they added four more prefixes
in 2022:  10^30, 10^27, 10^-27, 10^-30. I updated the issue to include them.

Unfortunately, as Stephen points out, they also get used when units are
combined such as kWh (which is really kW⋅h) and abused as kph (should be
km/h).

    Neil


On Tue, Nov 12, 2024 at 12:11 AM Joseph Wright <joseph@texdev.net> wrote:

> Hello Neil,
>
> Most but not all accepted SI units take prefixes: for example, BIPM
> specifically rule out min/h/day, but you can have dl (decilitre), mdB,
> etc. They are a bit vague about what is acceptable - so I'd say
> everything except time units is a possible.
>
> Regards,
>
> Joseph
>
>
>