Reste vs. restant
Both reste and restant translate to the English concepts of rest or remainder, but they serve slightly different grammatical and contextual roles. The word reste is the standard, everyday noun used for leftovers, remaining parts of a group, or what is left of an object. The word restant functions both as an adjective meaning remaining and as a noun that specifically emphasizes a remaining quantity, duration, or balance, often sounding slightly more formal or precise.
Reste
The noun reste is the most common and versatile word for the remainder of something, including food leftovers, the rest of a group of people, or physical remains. It is used in everyday situations to describe whatever is left over after a part has been taken, finished, or used.
Garde le reste de la tarte pour demain.
(Keep the rest of the pie for tomorrow.)
Que fait le reste du groupe ?
(What is the rest of the group doing?)
J'ai donné le reste de mon argent à mon frère.
(I gave the rest of my money to my brother.)
Les restes de ce château datent du Moyen Âge.
(The remains of this castle date back to the Middle Ages.)
Il a mangé ses restes de poulet froid.
(He ate his leftovers of cold chicken.)
Le reste du monde ne comprend pas cette blague.
(The rest of the world does not understand this joke.)
Restant
The word restant is frequently used as an adjective to mean remaining, but when used as a noun, it emphasizes a specific remaining quantity, financial balance, or duration of time. As a noun, it is less common than reste and is heavily featured in fixed expressions, particularly regarding the remainder of a lifespan or precise amounts.
Il va passer le restant de ses jours à la campagne.
(He is going to spend the remainder of his days in the countryside.)
Veuillez payer le montant restant avant le mois prochain.
(Please pay the remaining amount before next month.)
Le temps restant pour cet examen est de dix minutes.
(The remaining time for this exam is ten minutes.)
Il a versé le restant de la bouteille dans son verre.
(He poured the remainder of the bottle into his glass.)
Calculez le solde restant sur votre compte bancaire.
(Calculate the remaining balance on your bank account.)
Le restant de la marchandise sera livré demain.
(The remainder of the merchandise will be delivered tomorrow.)
Summary
In short, use reste as your default noun for the rest, leftovers, or remains in almost all everyday contexts. Choose restant when you need an adjective for remaining, or when you want a noun to specifically emphasize the remainder of a lifespan, a financial balance, or a precise measurable quantity.