How can I say "I want to" as a short response, omitting the main verb?

Question

If I am asked a question in English using want, for example:

Do you want to talk to me?

I can respond like this¹:

Yes, I want to.

I can't say:

Yes, I want.

It would be very incorrect and weird.

In Spanish, how can one say "I want to"?

Also, supposing this works, does it work with other verbs, for example "necesitar," to say "I have to" without a second verb?

¹_{Just "yes" works there, too; this is more formal.}

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Si alguien me pregunta algo en inglés, por ejemplo:

Do you want to talk to me?

Yo puedo responder con¹:

Yes, I want to.

No puedo decir:

Yes, I want.

Sería muy incorrecto y raro.

En español, ¿cómo se dice «I want to»?

También, ¿funciona la solución con palabras como «necesitar» para decir «I have to» sin un segundo verbo?

¹_{Decir sólo «yes» también funciona; este es más formal.}

Answer 1

Just say quiero. In a full reply you can say Sí, quiero. The verb doesn't work differently from other verbs. It doesn't have to indicate that an infinitive should follow when this infinitive is left out. So it's not like the English verb "to want" and others ("to like", "to love", "to plan", "to need", etc.).

—¿Quieres hablar conmigo?
—Sí, quiero.

Other Spanish verbs followed by infinitives work like this too:

—¿Te gustaría tomar algo? ("Would you like to have a drink?")
—Sí, me gustaría. ("Yes, I'd like to.")

There's no special word, similar to English "to", to mark an infinitive in Spanish. There are also no "phrasal verbs" in the English sense, consisting of main verb plus preposition/adverb; no verb in Spanish may appear followed by a dangling particle such as "to" in "I want to."

Note that some Spanish verbs that are customarily followed by an infinitive cannot simply leave it out, but have to replace it with the generic hacer plus the neuter pronoun lo.

—¿Planeas irte de vacaciones? ("Do you plan to go on holiday?")
—No, no planeo hacerlo. ("No, I don't plan to do it.")

Answer 2

Well Spanish doesn't work the same way as English in this regard.

In English you say I want to talk to someone, but in Spanish you say Quiero hablar con alguien. So you don't need any preposition or anything, so to the question

¿Quieres hablar conmigo?

the answer is

Sí, quiero.

Basically the infinitive of a verb doesn't require any additional word as the English "to". Other examples:

But, on the other hand:

• ¿Tienes que pasar por la tienda hoy después del trabajo? (Do you have/need to go to the store after work?)

In this case you cannot answer with sí, tengo nor sí, tengo que because both would feel incomplete. So the best answer would be either sí or sí, tengo que ir.

And also as a final note, a few examples on the difference between necesitar and tener que. Basically tener que refers more to an obligation, like the previous example with the visit to the store or this one:

Tengo que llevar a mi hija a su cita con el médico (I have to take my daughter to the doctor's appointment).

And necesitar is more used for something that needs special attention or certain urgency:

Necesito llevar el auto al taller (I need to take the car to the garage).

In this case you need to get the car repaired as soon as possible.

In this last example please note that the word car has many regional differences. Auto is used in the south countries of South America. Also the word taller could be taller mecánico or just mecánico.