Formal:
* Cheveux lisses: This is the most common and literal translation, meaning "smooth hair".
* Cheveux raides: This means "stiff hair" and is a bit less common.
Informal:
* Cheveux plats: This literally means "flat hair" and is a more colloquial way to say "straight hair".
* Cheveux droits: This means "straight hair" and is a more informal and direct translation.
You can also describe the hair texture using adjectives like:
* Lisse: Smooth
* Raide: Stiff
* Plat: Flat
* Droit: Straight
For example, you could say:
* J'ai les cheveux lisses. (I have straight hair.)
* Mes cheveux sont raides. (My hair is stiff.)
* J'aime les cheveux plats. (I like straight hair.)
Ultimately, the best way to say "straight hair" in French depends on the situation and your personal preference.