Why are French numbers so strange?
Well, there is one main reason: history.
Here, I’ll tell you the story of French numbers, made simple.
1: the Romans and the decimal system
The romans (like many Indo-European populations) counted with the decimal system (based on the number 10).
They colonized France around 50 BC and brought with them, their culture, language and their way of counting:
|20: VINGT||2 X 10|
|30: TRENTE||3 X 10|
|40: QUARANTE||4 X 10|
|50: CINQUANTE||5 X 10|
|60: SOIXANTE||6 X 10|
|70: SEPTANTE||7 X 10|
|80: HUITANTE||8 X 10|
|90: NONANTE||9 X 10|
2: the Celtics and the vigesimal system
But when the Romans arrived in France, they had to cohabitate with other populations that had already been there for ages.
The Gaulois are Celtics populations who were living in France since the 1st millenary BC.
Par QuartierLatin1968, The Ogre, Link
Celts in Europe
That should give something like that:
|30: VINGT-DIX||20 + 10|
|40: DEUX-VINGTS||2 X 20|
|50: DEUX-VINGT-DIX||2 X 20 + 10|
|60: TROIS-VINGTS||3 X 20|
|70: TROIS-VINGT-DIX||3 X 20 + 10|
|80: QUATRE-VINGTS||4 X 20|
|90: QUATRE-VINGT-DIX||4 X 20 + 10|
Another Theory says that this vigesimal system comes from the population of Denmark and Norway, the Normands, that arrived in Normandie around 900 AC.
3: the hybridization
Even if we are not sure of the origin of the vigesimal system, we can observe that both vigesimal and decimal system were cohabitating during the middle age in France.
It’s only during the 17th century, with the influence of the writers and intellectuals, that the Academy Française decided to choose the actual system, a hybridization of the decimal and vicesimal system.
10 : DIX
20 : VINGT
30 : TRENTE
40 : QUARANTE
50 : CINQUANTE
60 : SOIXANTE
70 : SOIXANTE-DIX
80 : QUATRE-VINGTS
90 : QUATRE-VINGT-DIX
4: In other French speaking countries
Not all the French speaking countries count that way.
– In Romande Switzerland, They use the complete decimal system.
– In Geneva and Belgium, they use the decimal system except for 80 that they pronounce quatre-vingt-dix (like in France).
– In Quebec and Francophone Africa, they count like in France.
Voilà! I hope you understand a little bit more the way we count in France. You can see that we like complexity ?
To finish, a nice map of the evolution of Indo-European language :