This is the 4756th most frequent French word.
préférés
"Préférés" means "preferred" or "favorites" in English.
'Préférés' describes 'livres' (books) in this sentence, being masculine plural to agree with 'livres'.
Les livres préférés de Marie sont exposés sur l'étagère.
Marie's favorite books are displayed on the shelf.
Here, 'préférés' is used as an adjective and agrees with the noun 'animaux' (animals), which is masculine plural.
Les chats sont mes animaux préférés.
Cats are my favorite animals.
'Préférés' is employed as an adjective and is tailored to match 'pommes' (apples), which is feminine plural.