In modern Spanish, the subjunctive mood is far more alive and less avoid-
able than in English or even some other Romance languages. Contexts do
occur in which the option sometimes exists of choosing between the indica-
tive and the subjunctive in Spanish, but this choice almost always implies
a change of meaning.
Whilst there are exceptions to general guidelines, it is possible to establish
some key characteristics of the subjunctive mood in Spanish. First, as its
name suggests, it occurs most frequently in subordinate clauses that are
joined(or at least linked) to a main clause in the indicative mood. Second,
whereas the indicative mood affirms actions or states that are already facts,
the subjunctive is commonly required in contexts which express hypotheses,
future possibilities, uncertainty, doubts, and desires for the future, although
this distinction is by no means absolute.
In modern Spanish there are only four tenses of the subjunctive in common
use: present, perfect, imperfect and pluperfect (for the forms see Chapter 10).Subjunctive in subordinate que clauses
The subjunctive occurs most frequently in subordinate clauses, which are
typically introduced by que. Some item in the main clause (often a verb)
will require the verb in the subordinate clause to be in the subjunctive.
This does not of course mean that all subordinate clauses will be in the
subjunctive mood. For example, compare Dudo que vengan (subjunctive)
‘I doubt they will come’ with Sé que vendrán (indicative) ‘I know they will
come’.12.1