I'll try ti esplain it to you
Generaly we put "S" at the end of the word like : ( table = tables / chaise = chaises ...)
But there are some exeption :
1- The words that end by "eu / au / eau" we put "X" except with this word : landau, sarrau, pneu et bleu we put "S"
2- the words that end with "ou" we put "S" in the plurel
but with this words we put "X" : bijou, caillou, chou, genou, hibou, joujou, pou.
3- the word that end with "AL" like "journal " we remove the "L" and we put "AUX" like
journal = journaux / cheval = chevaux
but we have an expetion with bal, carnaval, chacal, festival, récital, régal, cal, serval with this words we put "S"
4- the word that end with "AIL" we put an "S" but with émail, travail, et vitrail.
Un corail we evoid the "L" and we write "AUX"
travail = travaux
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