Verb modes vary according to the speaker's position in relation to the verbal action. In Portuguese, the following verbal modes are listed: Indicative, Subjunctive, Conditional, Optional and Imperative. O subjunctive mode it tends to raise doubts because it is easily confused with some conjugations of the indicative mode. We will, then, denote its particularities so that the doubts are clarified.
O subjunctive mode it is used in subordinate clauses when these express sentiment, hypothesis, probability, or uncertainty. Look at the examples:
Maybe I go to school tomorrow.
If they depart on the first flight in the morning, maybe get reach the destination today.
If I tell my story, no one would believe.
Have you noticed that when verbs are used in subjunctive mode, convey an idea of possibility, never certainty? Another characteristic of this verbal mode can be seen: its extreme dependence on another verb precisely because it is expressed in subordinate clauses that give meaning to the verbal action.
There are, in the subjunctive mode, the following tenses: present, past perfect, past tense, past tense more-than-perfect and future, standing out among them present, past imperfect and future, as they have some forms fixed construction. Note the examples based on the conjugation of the verb. go:
Present - indicates a possibility:
that I go
that you go
that he/she go
that we let's go
that you you go
that they/they they go
Imperfect past tense - indicates the possibility of the occurrence of a fact or not:
If I was
if you were you
if he/she was
if we we were
if you fossils
if they/they were
Future - indicates the possibility of an event coming to happen:
when I for
when you you are
when he/she for
when U.S let's go
when you you are
when U.S let's go
Therefore, whenever there is a verb indicating doubt or possibility, there will be an incidence of the mode subjunctive, which differs greatly from the indicative mode, as this is a verbal mode that expresses a fact or a assurance.
By Luana Castro
Graduated in Letters
Source: Brazil School - https://brasilescola.uol.com.br/gramatica/caracteristicas-modo-subjuntivo.htm