Material and Character
We can also use the preposition "de" to express the material of which something is made. A preposition is necessary when we do this in English, but we must use "de" when we talk about what something is made of Spanish.
"la puente de madera" (the bridge of wood, the wooden bridge);
"el cuaderno de cuero" (the notebook of leather, the leather notebook).
This usage has also extended to signify the matter or issue of something.
"el libro de geografía" (the book of geography, the geography book);
"hablábamos de la política" (we were talking of politics, we were talking about politics).
This same usage is also used to express the nature, condition, or character of a person. For example: "es un estudiante de talento" (he is a student of talent, he is a talented student).