[cetacea]

I think most other people use a single M to mean million, and k for thousand.

Can't we just use SI prefixes or spell the numbers out instead of using some random alternate convention?

[greglindahl]

This is not a "random alternate convention", it's a highly used convention that you aren't familiar with. I wasn't familiar with it, either, until I moved to the Silicon Valley. Now I see it all the time.

[wavefunction]

It's a ridiculous "convention" and it's dubious what you mean by "highly used."

Using Roman numerals for anything is a waste of everyone's time.

[jcrawfordor]

There exists a world of finance outside of Silicon Valley. M and MM to indicate thousands and millions are a finance convention, not an SV one, people in SV just happen to talk about finance a lot. Anyone in finance would be familiar with it, and given that the amount here is a dollar amount, the use seems perfectly fair.

[jonathankoren]

I strongly suspect that the page's etymology is wrong -- or more precisely -- not entirely correct. The Latin word for "thousand" is mille, which why the numeral for a thousand is M.

No one would be so asinine to mix numeral systems. Same thing with percent, which originally was rendered as "per-cent", as in "per hundred".

[nitrogen]

I don't think it's necessarily actually Roman numerals, but perhaps "mille", which means thousand. So thousand thousand means million.

[PhasmaFelis]

It's "highly used" in a specific field and nowhere else. Outside of that field, you should use broadly-accepted conventions.

[robbiep]

There is no Roman numeral m only M, so if they are sticking with convention shouldn't it be capitalised?

[jonathankoren]

Probably because it's not a numeral, but rather an abbreviation for mille.

[mulmen]

I completely agree with you, while I know $40+mm means $40M it is only because of context, not because I actually parse it as "thousand thousand". In my mind mm is millimeter, even as an American.

HN is the only place I see this notation used.

The great thing about standards is there are so many to choose from.

https://xkcd.com/927/