b. Forms of the verb used in the subordinate clause

I. Referring to present or future time
In a sentence containing a false or improbable condition, if the subordinate clause refers to present or future time, the Simple Past Subjunctive is usually used. In the following examples, the verbs in the Simple Past Subjunctive are underlined.
e.g. If it snowed, I would ski in the park.
If he were here, I would give him the books.
In these examples, the use of the Simple Past Subjunctive indicates that the subordinate clauses if it snowedand if he were here refer to present or future time.
In the case of a continuous, ongoing action, the Past Continuous Subjunctive may be used. In the following example, the verb in the Past Continuous Subjunctive is underlined.
If she were staying here now, I would let her ride my horse.
It should be noted that, in the case of the verb to be, in informal English, the Simple Past Indicative is often used instead of the Simple Past Subjunctive. For instance, the following pair of examples shows how the same idea might be expressed in formal and informal English.

Formal: If he were here now, I would give him the books.

Informal: If he was here now, I would give him the books.
It should be observed that, even when the Indicative is used instead of the Subjunctive, the use of a past tense for an action pertaining to present time, combined with the use of the conjugation with would in the main clause, is enough to indicate clearly that the condition expressed is considered false or improbable. However, this use of was instead of were is considered grammatically incorrect in formal English.

Ii. Referring to past time

In a sentence containing a false or improbable condition, if the subordinate clause refers to past time, the Past Perfect Subjunctive is usually used. In the following example, the verb in the Past Perfect Subjunctive is underlined.
e.g. If he had wanted to come, he would have called us.

In this example, the use of the Past Perfect Subjunctive indicates that the subordinate clause if he had wanted to come refers to past time. The use of the Past Perfect Subjunctive also indicates that the condition he had wanted to come is false.
In the case of a continuous, ongoing action, the Past Perfect Continuous Subjunctive may be used. In the following example, the verb in the Past Perfect Continuous Subjunctive is underlined.

e.g. If it had been raining yesterday, I would have taken my umbrella.

Iii. Summary

The forms of the Subjunctive most commonly used in subordinate clauses expressing false or improbable conditions are summarized in the following table.

Referring To	Verb in Subordinate Clause
Present or	Simple Past Subjunctive
future time	or Past Continuous Subjunctive
	e.g. If you started now, you would arrive on time.

Past time	Past Perfect Subjunctive
	or Past Perfect Continuous Subjunctive
	e.g. If you had started yesterday, you would have arrived on time.

c. Changing a statement containing a probable condition into a statement containing an improbable condition

A statement containing a probable condition can be changed into a statement containing an improbable condition, by changing the forms of the verbs.

For instance, in each of the following pairs of examples, the first statement contains a probable condition; whereas the second statement contains an improbable condition. The verbs in the subordinate clauses and main clauses are underlined.
Probable: If he is here now, we will give him the book.
Improbable: If he were here now, we would give him the book.
Probable: If I have time tonight, I will help you with your homework.
Improbable: If I had time tonight, I would help you with your homework.

In these examples, he is here now and I have time tonight express probable conditions; whereas he were here now and I had time tonight express improbable conditions.

These examples illustrate how, when referring to non-continuous actions in present or future time, a statement containing a probable condition can be changed into a statement containing an improbable condition. The verb in the subordinate clause is changed from the Simple Present Indicative to the Simple Past Subjunctive; and the verb in the main clause is changed from the Simple Future to the Simple conjugation with would.

It is sometimes said that when a verb is in the Indicative Mood, the use of a past tense indicates remoteness in terms of time; however, when a verb is in the Subjunctive Mood, the use of a past tense indicates remoteness in terms of probability.

The imperative mood

The Imperative Mood is used for giving commands. Like the Simple Present Subjunctive, the Imperative Mood of a verb is formed from the bare infinitive of the verb. For instance, the Imperative of the verb to work is work. In the following examples, the verbs in the Imperative Mood are underlined.
e.g. Work!
Work harder!
Likewise, the Imperative of the verb to be is be.
e.g. Be more alert!
You be ready to come with us.

The Imperative Mood can be used only in the second person. As shown in the first three examples above, the subject of the sentence is often omitted when the Imperative Mood is used. In such sentences, the subject youis said to be "understood". In written English, when the subject of the verb is omitted from a command, the command is often followed by an exclamation mark: !

The Imperative Mood can also be used in negative statements. Negative statements are formed using the auxiliary do, followed by the word not. The contraction don't is often used in spoken English. For example:

Without Contractions	With Contractions
Do not work so hard.	Don't work so hard.
Do not be afraid.	Don't be afraid.