In English, there are mainly three types of sentences.
- Simple sentence
- Compound sentence
- Complex sentence
A simple sentence has just one clause. A complex sentence has one main clause and one or more subordinate clauses. A compound sentence has more than one main clause.
We can change a simple sentence into a compound sentence or a complex sentence. This is usually done by expanding a word or phrase into a clause. In the same way, we can change a complex or compound sentence into a simple sentence. This is done by reducing a clause into a word or phrase.
Study the examples given below.
- It is too late to start a new lesson.
As you can see this sentence has just one clause and therefore it is a simple sentence. The number of clauses in a sentence is equal to the number of finite verbs in it. Note that to-infinitives and –ing forms are not finite verbs.
The structure too…to can be replaced by the structure so…that.
- It is so late that we cannot start a new lesson.
As you can see this sentence has two clauses: one main clause (It is so late) and one subordinate clause (That we cannot start a new lesson.) We have already learned that a sentence containing one main clause and one or more subordinate clauses is called a complex sentence.
Another example is given below.
- He worked hard that he might pass the examination.
The above sentence is an example of a complex sentence. It has one main clause (He worked hard) and one subordinate clause of purpose (That he might pass the examination). Subordinate clauses of purpose can be reduced to to-infinitives.
- He worked hard to pass the examination. (Simple sentence)
One more example is given below.
- He ordered that the traitor be jailed. (Complex sentence)
This sentence, too, can be converted into a simple sentence with the help of a to-infinitive.
- He ordered them to jail the traitor.