The “vicesimal” system, or why French people do math while counting

The “vicesimal” system, or why French people do math while counting

Everyone knows, the French language is one of the most bizarre languages in the world. It has rules there’s no way you can understand if you’re not a French passport holder, and we spend most of the time asking ourselves “WTF France”!?


Whether it’s the subjonctif impartait or plus-que-parfait, the sequence of tenses, the silent ‘h’ or the difference between ‘vert’ / ‘verre’ / ‘vers’ / ‘ver’, the French language has always posed a lot of problems for  students, but also for teachers. But least the basics are easy…aren’t they? Yeah, right!


Have you ever had to explain to your students how to count in French for example?


Teacher:          Dear students, today we’re going to learn to count in French. Repeat after me:


1 (un)               11 (onze)           20 (vingt)           50 (cinquante)
2 (deux)           12 (douze)         30 (trente)          60 (soixante).
3 (trois)            13 (treize)          40 (quarante)


Student:           Miss, how do you say seventy in French?

Teacher:            (WHY GOD, WHY?!)

If you’re one of those people who ask themselves why the French can’t simply say septante, octante and nonante like the Swiss, read on and we’ll tell you!


A little bit of history


In the Middle Ages, what is now France was populated by the Gauls (also called Celts). The Gauls lived in villages (that they called Oppidum) or in the countryside and they had a rich culture. They were great merchants, trading with their neighbours. Unfortunately, there isn’t much left of the Gallic culture today, and their language is more or less unknown.


What we do know is that Gaulish used the vicesimal numeral system. WTF is that you ask? The vicesimal or base 20 numeral system is based on the number twenty (just as the decimal system is based onten). Twenty corresponds to the number of fingers and toes that each human being has.


Simply put, Gaulish only had numbers up to 20 (twenty). To say 30, they would say “twenty-ten” (vingt-dix), and to say 40, “two-twenties” (deux-vingts). Sound familiar? 50 was “two-twenties-ten” (deux-vingt-dix) and 60 “three-twenties” (trois-vingts).

Looks like Gaulish was even more difficult than modern-day French. It could’ve been worse guys!


After the Middle Ages


Towards the end of the Middle Ages, the forms of the numbers evolved and we began to see the numbers trente, quarante, cinquante and soixante appear. It’s not clear why this stopped at sixty, perhaps because of a desire to retain something of the old languages that influenced French as we know it today.


In any case, this “mental calculation” which has us stumbling over soixante-dix (60+10=70), quatre-vingts (4*20=80) and quatre-vingt-dix (4*20+10=90) was officially adopted by the French Academy in the 17th century.


The forms septante, octante and nonante (official in Switzerland and Belgium) remain present in the spoken language. It is not forbidden to use these forms, but their use is not common in France.



Counting in French won’t get any easier after reading this, but now at least you know how these hellish forms came about. What do you think of the vicesimal numeral system? Should the French have kept this way of counting, or should  they go for septante, octante and nonate?


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Isidora Vlaovic
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