The subjunctive was formerly used in English for situations that were improbable or that expressed a wish. It is only rarely used in modern British English. It is, however, found in certain set phrases and in very formal forms of speech and writing.

God save the Queen!
God bless you!
God help us!
Heaven help us!
Heaven forbid that that should happen to me.
Suffice it to say he escaped with only a caution.

The present subjunctive

The form in the present tense is exactly the same as the base form in all persons of the verb. That is, there is no -s on the 3rd person singular.The subjunctive is used, in very formal English, in subordinate clauses that follow verbs expressing a desire, a demand, a formal recommendation, or a resolve.

I only ask that he cease behaving in this extraordinary manner.
It is vital that they be stopped at once.
Is it really necessary that she work all hours of the day?
I demand that he do something to make up for this.

The clause containing the subjunctive is linked to the main clause with that.

This use of the subjunctive is more common in American English than in British English. British speakers usually take advantage of other ways of expressing the same message, especially in less formal speech.

I only ask that he should cease behaving in this extraordinary manner.
It is vital that they are stopped at once.
It is vital to stop them at once.
Is it really necessary for her to work all hours of the day?
I demand that he does something to make up for this.

The past subjunctive

In written English and in very formal speech, the past subjunctive form were is sometimes used with the 1st and 3rd person singular, in place of the normal past form was.The past subjunctive may be used:

after if or I wish, to express regret or longing

If your father were alive he would help you.
If I were rich I would buy a Ferrari.
I wish I were taller.
If only he were here now!

after as if/as though and similar expressions, to express doubt or improbability.

You talk to him as if he were your slave!
Some people behave as though dogs were human.

Many people prefer to use the normal form of the past in this type of sentence. This is quite acceptable in ordinary English.

If your father was alive he would help you.
If I was rich I would buy a Ferrari.
I wish I was tall.
If only he was here now!
You talk to him as if he was your slave

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