[vram22]

Why the heck do people use 'bn' for billion and 'mm' for million? I've seen VC @fredwilson use 'mm' many times on his blog (avc.com), and IIRC I read some reasoning for it, either there or elsewhere, which made some kind of sense (they said Roman numeral for 1000 is M, so for million we use MM, though not sure if that is quite right logic), but why then the inconsistency between 'mm' and 'bn'?

[seanhunter]

I used to work in finance, and there is a bunch of obscure terminology and conventions, adopted from different cultures (eg you can trade a "Lakh" of silver).

See how the currency sign for GBP looks like a capital L? and the currency sign for shillings and pence was "s" and "d"? (now the uk use "p" for pence since decimalisation). So "Lire", "Soldi" and "Denarii" were the denominations of Italian currency in the the late Renaissance, and this obscure terminology was because originally the bankers in London were from Lombardy.

So I always thought MM was the same. For something like "Mille Mille" (ie one thousand thousands). I don't have any reference for this, that was just my own theory, and it's slightly undermined by the fact that the Italians have a word for "Million" ("Milione").

[toyg]

Loads of Latin and Italian words were modified across the world, not unlike what happens today with English; it's perfectly possible that accountants trading predominantly in the New World or some other remote area could have come up with their own approximation for a word (milione) that is not from Classic Latin and is actually pretty recent (wikipedia says XIII to XIV century, whereas lira and soldo are much older and denario goes all the way back to Rome fighting Carthage).

[vram22]

Ha, interesting. Didn't know about soldi. Coincidentally, had blogged (as an aside to my main post topic) about denarii recently. Here's what one looked like:

http://jugad2.blogspot.in/2016/07/the-many-uses-of-randomnes...

[vram22]

Good point. Yes, lakh (sometimes spelled lac) in English is from the Hindi word laakh, which I think is from Sanskrit laksha. (Many Indian languages are descended from or influenced by Sanskrit.)

[AjithAntony]

For anyone who is about to google this, a lakh is 100,000

[dgacmu]

The way to consistently use 'm' as thousand and 'mm' as million is if you assume a Latin derivation, with 'm' short for mille. https://en.wiktionary.org/wiki/mille#Latin ('mm' thus being 'thousand thousand', since roman numerals don't compose that way -- MM would be two thousand).

That doesn't mean that that's the way it evolved, but it's a way to categorize it mentally so it makes sense. While there's no logic for it conflating with 'million' and 'mega', at least 'mm' is fairly unique, unless you measure your money by its length.

[jegoodwin3]

That's true now but not in all historical periods. In the original system, m. was an abbreviation for mille, and not a composable component of the numeral at all. In effect, it served as a comma does in English text today, to separate the thousands from the units -- both of which were encoded using the composable letter system we are now familiar with.

Later, of course, people assimilated the operation of the M to the other letters, esp. on the dates of printed books. However, if we are discussing manuscript practice in the 15th century, the medieval approach and not the modern approach to Roman numerals would likely be in play...

In any event, using mm. to represent mille mille (a thousand thousand, a million in modern parlance) would create no cognitive dissonance as it does today.

[coldtea]

Because language and notation doesn't necessarily have to be logically consistent, just consistent in use.

[semi-extrinsic]

http://abstrusegoose.com/389