How do you say beautiful one in french?

There are two ways of expressing beauty. "Beau" is the masculine form & "belle" is the femmine form.

Ex.) Il est beau. This means; He is beautiful.

Ex.) Elle est beau. This means; She is beautiful.

Depending on weather the object is masculine or feminine depends on which form of it you should use.

Ex.) Ou est le cahier de maths? This means; Where is the math notebook. Because notebook is masculine, we use the "Il" form of it to answer the question. So the answer would be; Il est dans le sac a dos.