Definition of Subjunctive
At the request of grammar , the verbal mode that expresses the action of the verb with the meaning of doubt, desire or possibility is called a subjunctive . It is known as the virtual mode precisely because it offers the meaning of the verb but without updating . Traditionally, this verbal mode is used when wanting to account for uncertainty , subjectivity or possibility.
In the Spanish >expression of a desire (I would like my son to have a boy), expression of a doubt (I doubt that tomorrow comes to schedule), appearance in more or less fixed expressions (such is the case of: it is likely, it would be interesting that and it is likely that) and the expression of a negative order.
In those cases where the ruling verb imposes an idea of doubt on the subordinate sentence, the subjunctive mode must be used, instead, if the main verb imposes certainty, the subordinate sentence should be constructed from the indicative mode.
Likewise, all those verbs of desire, of order and of order will always require the use of the subjunctive mode, among the most common are: hopefully, wish, wait, want what, ask, beg and request that, propose and recommend that ...