If you mean "intelligent" or "clever":
* Intelligent: This is the most direct translation.
* Astucieux: This word implies cleverness and resourcefulness.
* Malin: This word implies a bit of cunning or slyness.
* Habile: This word implies skill and proficiency.
If you mean "stylish" or "fashionable":
* Chic: This is the most common translation for "smart" in this context.
* Élégant: This word implies elegance and refinement.
If you mean "smart" as in a "smartphone":
* Téléphone intelligent: This is the literal translation.
* Smartphone: This is the common English term, often used in French as well.
So, the spelling depends on the meaning you want to convey!