§ 170. Depending on the relation between the subordinate and the main clauses and on the use of tense and mood forms, complex sentences with conditional clauses may be subdivided into three types:

I. Complex sentences with clauses of real condition are those when the actions or events in both the clauses refer to the past or present and these actions or events are regarded as real facts. If the actions or events in these clauses refer to the future, the actions or events are regarded as possible real facts.

If f have offended you, I am very sorry.

Why did he send us matches if he knew there was no gas?

If Jules comes back, simply defy him to enter - that is all.

The conditional clause may be a statement for mere argument, no condition is meant.

If she got no money from her brother-in-law, she got what was as good as money - credit.

If Adrian had a passion, indeed, except for Diana Ferse, it was a burning desire to fix that breeding spot.

As can be seen from the above examples, the predicates in conditional clauses may be in the past or present indefinite, present perfect, present or past continuous.

II. Complex sentences with clauses of open condition. These clauses denote hypothetical situations or circumstances which may be (or may not be) realised in the present or future. Accordingly the subjunctive-mood forms are used both in the subordinate and the principal clause to denote actions or states.

In the main clause In the subordinate clause

1. Analytical forms with 1. The present subjunctive (be, go, see, etc.)

should non-perfect or the past subjunctive for all the

would infinitive persons in the singular and plural.

(in Modern English the Of these forms be and were can open

tendency is to use would asyndetically joined clauses.

for all the persons)

In case the state of the patient became worse he would be taken to a hospital.

If I were you, I would change into another dress.

You wouldn't be talking that way unless you were hurt.

2. Quasi-subjunctive-mood forms 2. The non-factual past indefinite

with may (might) + non-perfect infinitive and past continuous.

You might ask her this question if you were less scrupulous.

This might seem to be unreal unless I saw it with my own eyes.

3. The imperative mood. 3. Analytical forms with should + non-perfect

infinitive, (mostly with inversion).

Should he ask for references, tell him to apply to me.

II. Complex sentences with clauses of rejected condition imply non-fulfilment of the condition, as the actions or events described in the conditional clause refer to the past and the time of their realization is over. The condition is generally not even supposed to have been fulfilled, but is stated merely for the sake of argument. The following mood forms are used:

In the main clause In the subordinate clause

analytical forms non-factual past perfect

should

would

might + perfect infinitive

(may)

could

If I hadn't woken you, you'd (would) have lain there for the whole fortnight.

She would have been playing her part well unless she had been stiff with fright.

I might have persuaded her to change her mind if she had not been so obstinate.

If the book had been published they could have bought a copy in the shops.

Could he not have missed the train if he had been detained by the director?

The forms with may (might) and could are compound verbal modal predicates in the subjunctive mood.

The non-factual past perfect form may open an asyndetically joined conditional clause (with partial inversion).

Had the colour of the dress been to my taste, I should have bought it.

Had the world been watching, it would have been startled.