Lesson 7: Compound Sentences

Grammatical Form of a Compound Sentence

As described in Lesson 4, a sentence is highest ranked member in the Hierarchy of Grammatical Forms. In terms of the number of subordinate clauses in sentence, sentences can be classified into:

The following three sentences are simple sentences:

1. Water is a liquid.

Basic Declarative Sentence Pattern (1): S + V + sC

2. Water boils.

Basic Declarative Sentence Pattern (2): S + V

3. Water changes to steam.

Basic Declarative Sentence Pattern (3): S + V + A

As indicated, each sentence is a simple declarative sentence. A simple sentence is a sentence that does not have any subordinate (dependent) clause in the sentence.

Simple sentences can be combined with the help of conjunctions to form compound or complex sentences. In this lesson, we consider the compound sentences only. Complex sentences will be considered in Lesson 8.

1. Water is a liquid, and water boils.

2. Water boils, and water changes to steam.

Both sentences are compound sentence, in which two simple sentences are joined together by a coordinate conjunction “and”.

Coordinate Conjunctions

The following coordinate conjunctions are used to join simple sentences together to form compound sentences. They are known by FANBOYS, the acronym formed by their first letters.

In addition to the seven single-word coordinate conjunctions, there are the following two-word correlative conjunctions, which can also be used to join simple sentences into compound sentence.

In Lesson 1, all the above conjunctions have been used to join together like grammatical forms known as “parallel constructions”.

Examples of Compound Sentences Formed by Two Simple Sentences

Let us take the following two simple sentences

1. Water is a liquid.

2. Water can change into steam.

They can be combined into the following compound sentence:

Water is a liquid, and it can change into steam.

The two simple sentences are of the same rank in the Hierarchy of Grammatical Forms. If they are placed on an equal-arm balance, the balance is balanced as shown in the diagram below：

The use of punctuation marks should be noted. After the first main clause, a comma must be used, which is followed by the coordinate conjunction and then the second main clause. As an alternative, a semicolon “;” can be used instead of the comma. When the semicolon I used, the coordinate conjunction is omitted. So, the compound sentence becomes.

The following are compound sentences formed by two simple sentences:

(c) 2019 Augustine C. Chen