Puede (ser) que no nos hayan oído.
They may not have heard us.48.1.6 Quizá(s)/tal vez/posiblemente/probablemente/acaso+ subjunctive or indicative;
a lo mejor+ indicative
18.3.3 (p. 92); 49.1.3 (p. 293)
Quizá(s) and tal vez, ‘perhaps’, are equally common in informal as well as formal
registers, in spoken and written language. General usage of them seems to indicate that
they can be followed by a verb in the subjunctive or indicative, depending on the
degree of possibility involved, the indicative indicating a higher degree of possibility
than the subjunctive. This duality is especially true when reference is to the present,
or to the past – when this bears relationship with the present – as shown in the
examples below:Quizá(s)/tal vez esté en casa.
Perhaps he/she may be at home.
Quizá(s)/tal vez está en casa.
Perhaps he/she is at home.Quizá(s)/tal vez no nos hayan visto.
Perhaps they may not have seen us.Quizá(s)/tal vez no nos han visto.
Perhaps they have not seen us.When reference is to the future, most speakers seem to use the present subjunctive,
although the future indicative is also sometimes heard.Quizá(s)/tal vez se vayan/se irán mañana.
Perhaps they will leave tomorrow.Quizá(s)/tal vez se queden/se quedarán en un hotel.
Perhaps they will stay in a hotel.When quizá(s) and tal vez follow the verb, the indicative and not the subjunctive is
used.Va a llover, quizá(s)/tal vez.
It is going to rain, perhaps.No vendrán a la fiesta, quizá(s)/tal vez.
They won’t come to the party, perhaps.Posiblemente, like probablemente, ‘possibly’, ‘perhaps’, usually occurs on its own (see
48.1.1 above), but when followed by a verb, posiblemente normally takes the
subjunctive, while probablemente tends to be used with the indicative.Posiblemente lo vea. Perhaps I will see him.
Probablemente lo veré. I’ll probably see him.Acaso, ‘perhaps’, is a special case. In statements expressing uncertainty it is followed by
a subjunctive verb; it is formal in terms of register and rarely used in the spoken
language.Saying whether something is considered possible or impossible 48.1