The challenge of learning a new language isn’t just with the words.

As if learning the French language wasn’t perplexing enough, when you approach learning the numbering system, it can be way more baffling to learn than how to properly pronounce croissant.

So, it starts out easy enough, which gives you a false sense of hope. One, two, three: un, deux, trois…up to ten: dix. OK, good start. The next set, eleven, twelve, thirteen: onze, douze, treize…up to sixteen: seize, is pretty easy. Then you hit a little bump. 17 is dix-sept, (ten-seven), but, OK, I can go with that, then it’s dix–huit (ten-eight), dix–neuf (ten-nine). Great! I can do this. 20 is vingt, and 21 is vingt et un (twenty and one). But then 22 is vingt–deux (twenty-two), but what happened to the “et (and)” and now there’s a hyphen? In pursuit of the answers, I looked it up and found this bit of wisdom from the “conseil supérieur français de la langue française” (the French Higher Council of the French language): In 1990 a new spelling rule came into place where all numbers made up of two or more words, including large numbers, now need to be joined with hyphens (dashes).
21 = vingt et un (orthographe traditionnelle – traditional spelling)
21 = vingt-et-un (orthographe rectifiée de 1990 – rectified spelling as of 1990)

But, hang in there, that’s nothing. Keep on until you get to 70, and things get just plain goofy. Instead of a word for seventy, it’s soixante–dix, which is sixty-ten. And then 71 is soixante–onze: sixty-eleven, 72 is soixante–douze: sixty-twelve. What? Why? When you get to 80, it’s quatre-vingts: four twenties. Now we’re doing multiplication too? When you reach the 90s, if you haven’t yet thrown your lesson out the window, you probably will. 90 is quatre-vingt–dix: four-twenty-ten. And 97 is quatre-vingt–dix-sept: four-twenty-ten-seven. What the hell? I need a nap.

And then there’s the periods and commas. I’m used to writing a number over 1000 with a comma: 1,000, and then using a period for the decimal, if needed: 1,000.00. In French, you use the periods and commas in reverse, so, 1,000.00 would be 1.000,00. Commas are never used to separate thousands from hundreds but sometimes spaces are used (ten thousand is written 10.000 or 10 000, never 10,000), but they are used as a mark of decimals. 1.5 in English would be written 1,5 in French. OK, I’m game. Now to get back to the rest of the numbers. See you later.