A simple sentence consists of just one subject and one predicate. A compound sentence consists of two or more co-ordinate clauses, each of which has its own subject and predicate.

Compare:
Simple: Climbing up the tree, he plucked some mangoes. (One finite verb – One main clause)
Compound: He climbed up the tree and plucked some mangoes. (Two finite verbs – Two main clauses)

Here the simple sentence is transformed into a compound sentence by changing the participial phrase ‘climbing up the tree’ into the clause ‘he climbed up the tree’. Thus a simple sentence can be converted into a compound sentence by expanding a word or phrase into a clause and by using a coordinating conjunction to connect the clauses. More examples are given below:

Simple: Being ill, he didn’t attend the party.
Compound: He was ill and didn’t attend the party.

Simple: Besides being pretty, she is clever.
Compound: She is not only pretty but also clever.

Simple: In spite of his illness he attended the class.
Compound: He was ill, but he attended the classes.

Simple: He must run fast to catch the train.
Compound: He must run fast or he will not catch the train.

Exercise

Convert the following simple sentences into compound sentences:

1.    Being guilty he went into hiding.
2.    Being innocent, he never thought of running away.
3.    Besides being sent to prison, he was heavily fined.
4.    The old man sat in a corner, drinking.
5.    Owing to a friend’s intervention, he was later released from jail.
6.    Being lazy, he failed.
7.    He fled for fear of being arrested.

Answers

1.    He was guilty and went into hiding.
2.    He was innocent and never thought of running away.
3.    He was not only sent to prison but also heavily fined.
4.    The old man sat in a corner and drank.
5.    A friend intervened and he was later released from jail.
6.    He was lazy and failed.
7.    He feared that he would be arrested and fled.