Most adjectives ending in -al change to -aux (masculine plural) or -ales (feminine plural) - see Forming the plural of adjectives ending in -al - but there are exceptions to that rule.
Look at these cases:
The following adjectives are exceptions which take -s in the masculine plural form:
|Masculine singular||Masculine plural||English|
|banal||banals||banal / ordinary|
|bancal||bancals||wobbly / rickety|
|fatal||fatals||fatal / lethal|
|glacial||glacials / glaciaux||freezing|
|final||finals / finaux||final|
Both plural forms of glacial and final are accepted in French: regular (glaciaux / finaux) and irregular (glacials / finals)
Examples and resources
Q&A Forum 3 questions, 9 answers
Indeed, these examples are all feminine and plural forms of adjectives-
Des pierres précieuses = Precious stones
Des averses glaciales = Icy showers
Des boissons fraîches = Cold drinks
Des chemises chères = Expensive shirts
Des pommes rouges = Red Apples
Hope this helps!
Thank you Alan. That is exactly what I was asking. So fatal is fatales in Feminine Plural.
.....except in the very rare case when the adjective "banal" us used in its other meaning: feudal (as in the "feudal system"). In that case the plural masculin is "banaux": "les moulins banaux" = the feudal mills where peasants could mill their grain paying a fraction of it to the lord of the land.
-- Chris (not a native speaker).