When to use así que, por lo tanto in Spanish
To express the consequence/result of what is expressed in the main clause, we can introduce a subordinate clause with:
..., así que ...
..., por lo tanto ...
Have a look at the following examples:
Ana María no quiso venir con nosotras, así que se quedó en casa sola y aburrida.Ana María refused to come with us, so she stayed at home alone and bored.
Fernando suspendió el examen, por lo tanto no pudo pasar al siguiente nivel.Fernando failed the exam, therefore he couldn't move up to the next level.
You can see how, what is expressed after así que and por lo tanto is the result of the main sentence. Notice how we are using the indicative (not the subjunctive) in the result clauses.
With the subjunctive
However the subjunctive can also be used with these clauses if we add an element of possibility or doubt:
Mi tren lleva un poco de retraso, así que probablemente llegue tarde a la reunión.My train is a bit delayed, so I may be late for the meeting.
Mi jefa se ha ido de la empresa, por lo tanto puede que me den su puesto.My boss has left the company, therefore they may offer me her position.
Notice how when adding "posiblemente" or "puede que" (which add possibility and doubt) we use the subjunctive mood (llegue, me den).
Have a look at these other examples with the indicative and subjunctive:
He tenido una discusión con Sandra, así que no saldré con ella esta noche.I had an argument with Sandra, so I won't go out with her tonight. (indicative)
He tenido una discusión con Sandra, así que, lo más seguro es que no salga con ella esta noche.I had an argument with Sandra, so it's most likely I won't be going out with her tonight. (subjunctive)
El guiso se ha quemado, así que pedimos unas pizzas.The stew is burnt, so we are going to order some pizzas. (indicative)
El guiso se ha quemado, así que posiblemente pidamos unas pizzas.The stew is burnt, so we might order some pizzas. (subjunctive)
If there are no elements/particles expressing doubt/probability/possibility, result clauses introduced by así que / por lo tanto are followed by the indicative.
Bear in mind that although the most common result connectives are "así que" and "por lo tanto", other constructions can introduce result clauses in Spanish. For example:
- conque...
- de manera que...
- de modo que...
- luego...
- por consiguiente...
- como consecuencia...
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