I am writing a card to an adult so do I use

Le deseo or la deseo? Normally te deseo would refer to a friend.....so to be formal which do I use?
Le is indirect object and se is direct object right?
My answer: la deseo

Le deseo

If you are studying castellano and therefore use leísmo, the Direct Object would be "le deseo" for a man and "la deseo" for a female.

Leísmo: Leísmo ("using le") is a dialectal variation in the Spanish language that occurs largely in Spain. It involves using the indirect object pronoun le in place of the (standard) masculine direct object pronoun lo, especially when the direct object refers to a male person.

However, you "might" use the Indirect Object Pronoun "le" if your meaning is: I wish FOR YOU...

In any even, you are correct that Te deseo IS familiar and not to be used here.

Sra

When referring to an adult in a formal context, you would use "le deseo" instead of "la deseo."

In Spanish grammar, the third person singular pronoun "le" is used as the indirect object pronoun, while the third person singular pronoun "la" is used as the direct object pronoun for feminine nouns.

To determine whether to use the direct or indirect object pronoun, it is important to understand the context and the action being performed. If you are directly wishing or expressing desire towards the person, you would use the direct object pronoun "la." However, if you are indirectly wishing or expressing desire towards the person, you would use the indirect object pronoun "le."

In the case of your question, since you are writing a card and directly wishing or desiring something for the adult, you would use the direct object pronoun "la." Therefore, the correct phrase would be "la deseo."

Remember, using the correct pronoun is essential to convey your message accurately and respectfully.