Use: A. Simple Sentence

In simple sentences only Subjunctive I is used in a few set expressions as a survival of old usage (the so-called formulaic expressions).

1. Most of them express a wish:

Long live the Army!

Success attend you!

Be yours a happy meeting!

Far be it from me to spoil the fun / to conceal the truth.

Suffice it to say that he is a liar.

God bless you! God save the Queen! Heaven forbid!

Confound your ideas!

Subjunctive I in such expressions can be replaced by “may + Infinitive”:

May success attend you! May your meeting be happy!

May the Army live long!

2. Some formulaic expressions have a concessive meaning:

Happen (come) what may (will).

Cost what it may.

So be it (Be it so).

Subjunctive I in these expressions may be replaced by Let + Infinitive:

Let it be so.

3. The only productive pattern of a simple sentence with Subjunctive I is the sentence expressing a command or a request with an indefinite pronoun as the subject:

Everybody leave the room!

Somebody switch off the light!

Subjunctive I may be replaced in such sentences by “let + Infinitive”:

Let everybody leave the room.

4. The Suppositional Mood is used only in one type of interrogative sentences beginning with And what if …? (А что если вдруг …?):

And what if he should come back?