This is the 2471st most frequent French word.
vieux
Old.
In this sentence, 'vieux' is used as an adjective to describe the noun 'chien,' indicating age.
Mon vieux chien adore se reposer.
My old dog loves to rest.
The word 'vieux' serves as an adjective modifying the noun 'livres,' denoting antiquity or age.
Ces vieux livres ont une grande valeur historique.
These old books have great historical value.
'Vieil' is the masculine singular form of 'vieux' used before nouns starting with a vowel sound or mute 'h,' thus modifying 'ami' here.