Present subjunctive (e.g.: Quero que fales)

Questions about the Subjunctive

Q: Why is it Quero que tu saias and NOT Quero que tu sais?
The subjunctive stem is based on the present “eu” form. Since the present of sair is eu saio, the subjunctive stem is sai- → saias.

Q: Why is it … depois que o faço and NOT … depois que o faça?
The expression depois que is followed by the indicative, while antes que is followed by the *subjunctive. This reflects certainty: events after they happen (depois) are real, while events before they happen (antes) are uncertain.

Q: Why is it Acho que ele vem and NOT Acho que ele venha?
The verb achar (like crer) is followed by the indicative in affirmative sentences, but by the subjunctive in negative ones:

• Acho que ele vem.

• Não acho que ele venha.

Q: Why is it Não penso que ele saiba and NOT Não penso que ele sabe?
The verb pensar is followed by the subjunctive in negative sentences and by the indicative in affirmative ones:

• Penso que ele sabe.

• Não penso que ele saiba.