Numbers
Learning numbers will be crucial in situation like telling time, buying things, and counting anything you want.
From 61 to 99, the base 20 is used (inheritance from Celtic languages)
☞ 70 : soixante-dix [60+10]
☞ 79 : soixante-dix-neuf [60+10+9],
☞ 80 : quatre-vingts [4*20]
☞ 90: quatre-vingt-dix [4*20+10]
The number 80 (quatre-vingt) only takes an s in round numbers
☞ 80 : quatre-vingts
☞ 280 : deux cent quatre-vingts
It also takes an s when followed by a noun:
☞ Le tour du monde en quatre-vingts jours. Around the world in eighty days.
It is invariable for all other numbers
☞ 82 : quatre-vingt-deux
The number 100 cent only takes an s in round numbers
☞ 200, 300 etc. : deux cents, trois cents etc.
For all other numbers it is invariable
☞ 611 : six cent onze