Spanish Lessons


Expressing Possibilty

Our previous lesson explored the use of the verbs haber and deber to express obligation, requirement, or necessity. Let's now see how we can used them to express possibility or supposition instead.


We learned that the construction haber + de + infinitive is used to express obligation or necessity. The following example, however, shows that it's also possible to use it to express possibility:

Si mi vida ha de continuar... será por ti

If my life should continue... it will be for you

Captions 7-10, Belanova - Por ti

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Of course, as you may have noticed, the use of the conditional si (if) plays an important role here. By using it, a sentence that would otherwise express a certain necessity, like mi vida ha de continuar (my life should continue), is transformed into one that expresses possibility. We can also use other words or phrases besides the conditional, for example, words typically used to express possibility, supposition, conjecture, or doubt. Here is an example using tal vez (maybe):

Tal vez ha de haber sido... un intento de mi parte.

Maybe it must have been... an attempt on my part.

Captions 24-25, Arturo Vega - Entrevista - Part 4

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However, sometimes we have to figure it out by the context. See for example this fragment of the song Marciano (Martian) by Mexican band Molotov:

No es el cuerpo marrano que solía tener, ni la cara, mi reina, que tú has de querer.
It's not the fat body I used to have, nor the face, my queen, that you probably want.

In fact, English is not unfamiliar with the use  of "should" and "must" to express probability in sentences that rely on context for interpretation. Here are two examples:

Ha de tener hambre. | She must be hungry.
Has de querer que te de dinero. | You must want me to give you money.

You must also know that the expression ha de ser by itself means "perhaps" or "maybe":

Creo que ella es la ladrona. -Sí. Ha de ser.
I believe she is the thief. -Yes. Perhaps.

More interesting yet is the use of the verb deber (which is also a noun meaning "duty") to express possibility in Spanish. In our previous lesson you learned that deber + infinitive is used to express obligation. You also learned that it's grammatically incorrect, though common, to use deber + de + infinitive for the same purposes: you mustn't say debes de hacer la tarea, you must say debes hacer la tarea (you must do your homework). This is because deber + de + infinitive is reserved in Spanish to express possibility. Here are some examples:

Ah el... Este debe de ser el contrato.

Oh the... This must be the contract.

Caption 15, Muñeca Brava - 9 Engaños - Part 9

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So, in the case of the verb deber, Spanish uses two slightly different constructions: debe de + infinitive for possibility, and debe + infinitive for obligation. Compare the previous example with the following:

Yo insisto en que éste debe ser el contrato.
I insist that this must be the contract.

Here is another example where debe de is correctly used to express possibility: 

Así que creo que le debe de haber sido muy difícil.

So I believe that it must have been very hard for her.

Caption 47, Biografía - Natalia Oreiro - Part 6

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But, as we mentioned before, the use of debe de + infinitive instead of debe + infinitive to express obligation is a very common mistake. We should avoid doing it, especially in written or formal Spanish. Not that it's a big deal, but below is one example (and you can find many more similar cases by searching our catalog): 

Y esto lo debe de pagar* el cliente porque es de otro siniestro.

And this must be paid by the customer because it's from another accident.

Captions 17-18, 75 minutos - Gangas para ricos - Part 20

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*Y esto lo debe pagar el cliente is the correct expression.

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Caption 10, 9, 8, 7

Using haber de to Express Necessity or Possibility

The expression haber de followed by an infinitive verb usually means "to have to," "to be necessary," or "to be supposed to." This phrase is similar to tener que or haber que, but it expresses a much weaker and often vague sense of obligation. Haber de can and is used in normal speech, but is more likely found in literature and song lyrics.


In one of her videos, Raquel uses haber de to explain how to open a bank account:


Siempre hemos de asistir personalmente a la entidad bancaria para poder realizar la firma de todos los documentos originales.

We should always go personally to the banking entity to be able to do the signing of all the original documents.

Captions 13-14, Raquel - Abrir una cuenta bancaria

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You can also find the expression in Muñeca Brava's musical theme, sung by Natalia Oreiro:


Que la suerte sea suerte y no algo que no he de alcanzar

So that luck becomes luck and not something that I can't reach

Caption 4, Muñeca Brava - 1 Piloto

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Also, in our Mexican movie, El Ausente we hear Valente Rojas daringly say:


En un minuto nací y en menos he de morir.

In one minute I was born and in less [than that] I shall die.

Captions 8-9, El Ausente - Acto 4

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Since haber de expresses a milder sense of obligation or necessity, it's perfect to make a polite recommendation; it's less imposing than tener que or haber que:


Lo primero que has de hacer al reservar en un restaurante es: Saludar.

The first thing that you have to do upon reserving at a restaurant is: To greet [the people there].

Captions 3-4, Raquel - Reserva de Restaurante

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In the previous example, Raquel could have also said: Lo primero que tienes de hacer or Lo primero que hay que hacer (Remember that haber que is only used with the impersonal form of the verb haber: hay (present) or hubo (past).) Haber de is simply more polite, even poetic.

Finally, you should know that haber de is sometimes used to express possibility, for example to make a supposition:

Tal vez ha de haber sido... un intento de mi parte por... conceptualizar... a... la sociedad norteamericana, ¿verdad?

Maybe it must have been... an attempt on my part to... conceptualize... the... American society, right?

Captions 24-26, Arturo Vega - Entrevista

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¡Deben de haber aprendido mucho con esta lección! Thanks for reading!

Second Hand Meanings

Arturo Vega moved from Mexico to the U.S. decades ago, so he's very well versed in all sorts of Americana. In fact, in our Spanish-language interview, he's occasionally searching for the right Spanish word, when the English one is at the tip of his tongue. For example, when Vega described a beloved belt buckle featuring an eagle that looked like it was made by "drunk Vikings," he asks his interviewer for help finding the right word.


Listen in:


Yo tenía un cinturón... que lo compré en una tienda del ejército, de esas de... cómo se dice, de

"surplus", de, de desperdicios, de...

I had a belt... that I bought at an army store, one of those... how do you say, of

surplus, of, of leftovers, of...


-De segunda.



De segunda, con un águila muy grande. Era de una banda militar.

Second-hand, with a very big eagle. It was from a military band.

Captions 45-50, Arturo Vega - Entrevista - Part 4

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In the U.S., we all know about Army-Navy surplus stores, where you can find fatigues, drab-olive jackets and eagle-blazoned belts. But selling military surplus to the public for discount prices is not a common practice in many other countries, hence the struggle for words here. Vega says "surplus" in English, which is usually translated as "excedente" in Spanish. But Vega follows up with "desperdicios" which translates as "waste," "scraps" or "leftovers" -- as in, "desperdicios sólidos" ("solid wastes").


Hearing his search for words, our interviewer jumps in with "De segunda" -- which is short for "de segunda mano" ("second hand"). Now, second-hand stores are known the world over. Although Vega must know that second-hand is a bit different than Army-Navy surplus, but he's simply trying to tell a story here. In other words, the belt was cheap, OK? And from that cheap belt came Vega's inspiration for the famous logo for the Ramones.


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Caption 50, 49, 48, 47, 46, 45

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