Formal:
* Cœur brisé: This is the most literal translation and is considered formal.
Informal:
* Le cœur brisé: This is the more common way to say it in everyday conversation.
* Le cœur en miettes: This translates to "heart in crumbs" and conveys a more intense feeling of brokenness.
* Avoir le cœur brisé: This means "to have a broken heart" and emphasizes the experience of feeling heartbroken.
You could also use more figurative expressions like:
* Avoir le cœur déchiré: This translates to "to have a torn heart" and emphasizes the pain of the broken heart.
* Avoir le cœur à l'envers: This means "to have the heart upside down" and expresses a feeling of being turned inside out by the pain.
The best way to say "broken heart" in French depends on the context and the level of formality you want to convey.