French Phrase
Ça sert à quoi, blanchir ?
Meaning
Literally, "What is it used for, whitening?" It asks about the purpose or function of the act of whitening—whether it’s teeth, laundry, or any other object. The tone is informal and often heard in everyday conversation.
When to use
Use this phrase when you want to inquire about the benefit or purpose of a whitening process, such as a new whitening toothpaste, a laundry detergent, or a cosmetic treatment. It’s suitable in casual settings with friends or family.
✦Grammar Breakdown
Çasertàquoi,blanchir?
Ça sert à quoi
The construction "ça sert à + infinitif" means "it is used for …"; when turned into a question, "ça sert à quoi" asks "what is it used for?"
Infinitive as a noun
In French, an infinitive can function like a noun. Here "blanchir" (to whiten) is the subject of the question, equivalent to "the act of whitening".
Punctuation
A comma before the infinitive is optional but common in spoken French to signal a short pause.
🗨In Conversation
J’ai acheté ce nouveau dentifrice blanchissant.
I bought this new whitening toothpaste.
Ça sert à quoi, blanchir ?
What does whitening do?
✕Common Mistakes
Ça sert pour quoi, blanchir ?
The idiomatic question uses "à quoi" after "servir", not "pour quoi".
Ça sert à quoi, le blanchir ?
If you want a noun, use "le blanchiment"; using the infinitive is informal.
Ça sert à quoi, blanchir
Missing the question mark changes the tone; always end with a question mark in written French.
↔Alternatives
À quoi sert le blanchiment ?
What is bleaching for?
Quel est l’objectif du blanchiment ?
What is the goal of bleaching?
Pourquoi blanchir ?
Why whiten?
Cultural Tip
In French, "blanchir" can refer to teeth, laundry, or even skin. The phrase is informal; in a professional context you might replace it with "Quel est le but du blanchiment ?" Also, avoid using "pour quoi"—the correct idiom is "ça sert à quoi".