Nouns ending with –al see their suffix turn to –aux in the plural form. Once again, let’s look at some examples:
Un cheval (a horse) Les chevaux (the horses)
There are, however, some exceptions to this rule (singular/plural):
Aval/avals, bal/bals, cal/cals, carnaval/carnavals, chacal/chacals, festival/festivals, naval/navals, pal/pals, récital/récitals, régal/régals.
Simply add an “s” for the plural form of those exceptions.
Nouns ending with –eau, -au, -eu change to –eaux, -aux, -eux, in their plural form.
Some examples :
Un tuyau (a pipe), les tuyaux (the pipes)
Un feu (a fire), les feux (the fires)
Once again, there are some exceptions to this rule. When it comes to the following exceptions, simply add an “s” to the singular form to turn them into the plural form (singular/plural).
Landau/Landaus, sarrau/sarraus, bleu/bleus, pneu/pneus,