Can someone justify why is million written mm or MM?

Writing million as "mm" or "MM" doesn't make sense because billion is abbreviated as "bn" or "b".

"but 'mm/MM' is roman for million because each 'm' is one thousand, so 'mm' is one thousand times one thousand = million" -- then why not write 'mmm' for billion? Or why not just 'm' for thousand instead of 'k'?

"but 'mm' sounds like million" -- there's only one 'm' in million and under that logic, 'mn' would still be better

When most use "k" for thousand and "bn" or "b" for billion, it doesn't make sense to use anything other than "mn" or "m" for million. If you saw "mn", wouldn't you first assume it meant million?

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Writing "mm" for million does make sense because "m" is Roman numeral 1,000 and 1 million is 1,000x1,000.  It would be confusing to write "mm" and "mmm" for bln, so it's "bln" or "bn" so it's easier to distinguish btwn the two.  As for "mm" vs "MM" it's a firm/personal preference, but "mm" looks much cleaner.

I come from down in the valley, where mister when you're young, they bring you up to do like your daddy done
 

The only people who ever argue with this are Americans who have rarely/never dealt with the metric system lol

"If you don't have any enemies in life you have never stood up for anything" - Winston Churchill | "It's a testament to the sheer belligerence of the profession that people would rather argue about the 'risk-adjusted returns' of using inferior tooth cleaning methods." - kellycriterion
 

Quo aut et quam ipsa. Dolorum qui autem velit distinctio facilis voluptatem.

In hic facilis delectus consequatur. Sequi vero culpa nulla reiciendis consectetur. Omnis vero ad eligendi pariatur minus voluptatibus autem. Consectetur rem voluptatem sed ab.

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