Cuando estás hablando sobre algo que podría ocurrir condicionalmente, se puede usar el subjuntivo:

A menos que estudies, no aprobarás.

Pero igual se puede usar el indicativo con "si no":

Si no estudias, no vas a aprobar.

Aunque puedes usar los dos, "si no estudies" o "a menos que estudias" suena muy raro. ¿Por qué se puede expresar el mismo pensamiento en dos maneras tan diferentes?

  • 1
    The first option is expressing an opinion, something hypothetical. In the second option you’re affirming a belief. ‘Unless you study, you won’t pass’. ‘If you don’t study, you will not pass’. spanish.stackexchange.com/questions/31315/…
    – Traveller
    Commented Sep 18, 2019 at 9:45
  • @Curtis, Pero is not always the best word to translate but. You could use Sino (even if pero and sino used to be synonyms) or Mas (without accent).
    – VeAqui
    Commented Sep 21, 2019 at 3:31

2 Answers 2


En el libro "Gramática española: simple, compacto y claro" de Heike Pahlow, Silvia Martín Jiménez, Itziar Andraca Riffard, Blanca Lou Cotolí encontramos un listado de conjunciones condicionales, de acuerdo con el cual sólo se usa indicativo con "si" y "si no" y subjuntivo con el resto de las conjunciones:



Las formas "si no estudies" o "a menos que estudias" no son gramaticales.

El motivo por el cual "si no estudias" usa indicativo y "a menos que estudies" usa subjuntivo podría ser que la primera contiene una afirmación, mientras que la segunda es pura condición:

  • Si no estudias (no estudias, y en caso de persistir en esa actitud), no vas a aprobar el examen.
  • A menos que estudies, no vas a aprobar el examen (sólo aprobarás en la eventualidad de que estudies).

I think this is one of the few occasions when looking at the version in another language may help.

You would say

if you do not study, you will not

expressing something almost timeless which applies in the past, now, and in the future.

If you say

unless you study, you will not

you are talking about something hypothetical. After all s/he might study and then none of it will come to pass, indeed that is the whole point of the advice.

  • Both of them offer the opportunity for the individual to change the outcome by studying though, surely - neither is saying "as you haven't studied, you will not" which I can see would be a different thing. Commented Sep 18, 2019 at 11:57
  • @Curtis Parfitt-Ford It’s about conveying the speaker’s view - by using the indicative the speaker is asserting a belief. Using the subjunctive conveys a hypothesis and therefore lack of that certainty. The speaker chooses which to use depending on what they want to communicate.
    – Traveller
    Commented Sep 18, 2019 at 23:17

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