Verb taking a direct object–for example, “Say something. I really want a slice of cake, but I’m supposed to be on a diet. Querría un trozo de pastel, pero se supone que estoy a dieta. This sentence all That I Want not a translation of the original sentence.
Tengo ganas de un trozo de pastel. I want to be a doctor when I grow up. Quiero ser médico cuando sea mayor. Refers to person, place, thing, quality, etc.
For want of a knife, he cut with his fork. A falta de un cuchillo, lo cortó con el tenedor. He looked at her with want in his eyes. Phrase with special meaning functioning as verb–for example, “put their heads together,” “come to an end.
I want you to tidy your room. Verb not taking a direct object–for example, “She jokes. I want you here by nine o’clock tonight. Quiero que estés aquí para las nueve de la noche.