"Le Plus" is French for "most".
qui est le plus âgé? who is the oldest?
It means "the happiest" in French.
"qui aime le plus l'école ?" means "who likes school best?" in French.
"the smallest country"
"C'est moi le plus fort" means 'I am the strongest' (or 'the best') in French.
The happiest of men
Le fémur esst l'os le plus long.
It means "Hello, most beautiful/handsome"
what is the biggest of the carnivores
a night sweeter than the day
The contraction for "de plus le" is "du".
Vous êtes la plus magnifique tante. You are the most magnificent aunt.