‘If I make a promise, I keep it’- this sentences represent general validity and “If” here corresponds to “When”(Whenever). Such conditional sentences are used in factual discussions.
Subjunctive mood expresses a condition which is doubtful or not factual.
For example, “If don’t disapprove your work”, i.e. if I don’t act in a certain manner, and we want to state what the effect of it would be we you “If I didn’t” – Subjunctive mood – “Too bad I didn’t disapprove your behavior, If I did you would have been more respectful now”, or “It’s too bad I don’t exercise daily. If I exercised daily I would be healthier.” “Would” is used to show habitual action, i.e. I would be in a different context. This condition may or may not be fulfilled, and we make such statements when the action in the conditional clause “is being actively considered” or “likely to happen”. This type of condition is also called “probable”, nonetheless it should be noted that the probability of the condition is only in the speaker’s mind.
Let’s consider another example “If we by any chance missed the ten o’clock train, we would get there only after lunch.” In this sentence Subjunctive Mood is used in a statement which is a condition of “remote possibility”, i.e. it refers to an imaginary present rather than an actual past.
The verb form used in the Subjunctive Mood to make statements about an “imaginary present” is the same Past Indicative form, which is used to make statements about an actual past.
“If we by any chance had missed the 10 o’clock train we would have gotten there only after lunch” – this statement refers to “an imaginary past”.
The subjunctive Mood is formed using Past Participle form of the main verb – used for statements about an actual Past Perfect, which is a step further back into the past.
Very often a wrong tense is used for the “If clause”, i.e. “If I would miss…”and such errors are common.
The subjunctive Mood – “If I/you/he were, then… would be…”, and “If I/you/he/she had been, then… would have been” – occurs in both “If-clause” and the second – “I would…” but the verb forms used in each clause are of different tenses. Note that “If-then” statements are about the future, which in American English are usually in Indicative Mood rather than Subjunctive Mood: If A happens, then B will happen. The British often use Subjunctive Mood for the “If-clause”, e.g. “If A should happen, then B will happen”.
The example “If you would pay me, I would be grateful to you” is correct, which may seem to contradict the above point. However, “would” in the first clause is not just an auxiliary verb, as it is in the second clause—it has a meaning “to wish” or “to be willing”. “Would” can also be omitted in this sentence – “If you paid me, I would be grateful”. Note that “I wish you would have paid me” is an error, it should be “I wish you had paid me”.
“I wish I were rich” and “I wished I were rich” are both correct. In this case—the Indicative verb “wish” is followed by a subjunctive clause. The tense of the subjunctive verb is not affected by the tense of the indicative verb. Similarly, “He wishes he had been elected a major”, “He wished he had been elected a major” and “He will wish he had been elected a major” have similar subjunctive clauses.
“He acts as if he were rich”, “He acted as if he were rich”, and “He will act as if he were rich” are also correct, and so are “He acts as if he had been elected a major”, “He acted as if he had been elected a major” and “He will act as if he had been elected a major.
A clause beginning with “as if” or “as though”, unlike a clause beginning with “If”, is typically dependent on an indicative clause, and the tense of the indicative verb in that clause has no effect on the tense of the subjunctive verb in a subjunctive dependent clause.
I occasionally see errors such as “He had acted as if he had been rich”.
Some clauses beginning with “As if “or “As though” are not subjunctive: “It looks as if it will rain”, “She acted as though she was desperate”. These clauses express what the speaker believes is true or probably true and are not truly subjunctive in meaning, yet the subjunctive is often used in such cases.