Same message, different tone
You know deber, poder and querer in the present. Put them in the conditional, or querer in the -ra imperfect subjunctive as quisiera, and the content stays the same. What changes is how hard you push, how sure you are and how polite you sound. English does this with separate words: must → should, can → could, I want → I'd like.
Direct and softened
Present - direct
Debes hablar con ella.
You must talk to her.
Puedes preguntar en recepción.
You can ask at reception.
Quiero hablar con el responsable.
I want to speak to the person in charge.
Conditional / quisiera - with distance
Deberías hablar con ella.
You should talk to her.
Podrías preguntar en recepción.
You could ask at reception.
Quisiera hablar con el responsable.
I'd like to speak to the person in charge, please.
debe or debería: obligation or advice
Debe states an obligation: a law, a rule, something that is not optional. Debería gives advice and leaves the decision to the other person. Looking back, debería haber + participle becomes a reproach or a regret: should have. In elevated writing you will also see debiera instead of debería.
El inquilino debe avisar con un mes de antelación.
The tenant must give one month's notice.
A contractual obligation.
Deberías dormir más, se te ve agotada.
You should get more sleep, you look exhausted.
Advice between friends.
Deberías haberme avisado antes.
You should have told me sooner.
A reproach, looking back.
La administración debiera revisar estos plazos.
The authorities ought to review these deadlines.
Elevated written style.
puede or podría: possibility and suggestion
Puede says that something is possible or allowed. Podría makes the possibility less certain and turns an instruction into a suggestion. With haber + participle, podrías becomes a reproach: you could have.
Con este tráfico, puede llegar tarde.
With this traffic, he may well be late.
A realistic possibility.
Podría llover por la tarde, aunque no es probable.
It could rain in the afternoon, though it's unlikely.
A remoter possibility.
Podríamos dejarlo para el lunes.
We could leave it until Monday.
A suggestion, not a decision.
Podrías haber llamado, ¿no?
You could have called, couldn't you?
A reproach, looking back.
quiero, querría, quisiera: three steps
Quiero is perfectly normal among people you know, but with strangers or a boss it sounds demanding, just like I want in English. Querría is the conditional and softens the wish. Quisiera is the usual polite form with strangers, at work and in letters. This -ra form of the imperfect subjunctive stands here in a main clause, with no trigger before it.
Degrees of politeness
| Form | Effect | English |
|---|---|---|
| quiero | direct, demanding with strangers | I want |
| querría | softened | I would like |
| quisiera | polite, reserved | I'd like, I was hoping to |
Quisiera pedirle un favor.
I'd like to ask you a favour.
Quisiera cambiar la cita del jueves, si es posible.
I'd like to move Thursday's appointment, if possible.
Querría saber cuánto tarda el envío.
I'd like to know how long delivery takes.
