What is a compound sentence in English?

This is the fourth of eight lessons about Sentence Structures. To complete this course, read each lesson carefully and then unlock and complete our materials to check your understanding.   

– Focus specifically on compound sentence structures

– Outline the four considerations of compound sentences

– Provide examples to guide the learner’s understanding

Lesson 4

Compound sentences such as ‘I like studying, and he likes tennis.’ are probably one of the most common of the four sentence structures. Because of this frequency, it’s therefore important to understand how to use compound sentences – particularly in academic writing. Much like the rules for simple sentences, the following four rules for complex sentences should be followed at all times.


1. Use Only Independent Clauses

Both simple sentences and compound sentences are only composed of independent clauses (remember that an independent clause generally has a subject and a verb and may stand alone as a complete sentence). If a sentence contains a subordinating conjunction such as ‘because’ or ‘even though’ and therefore contains a subordinate clause, it’s not a compound sentence.


2. Use Two or More Independent Clauses

Unlike a simple sentence, compound sentences require two or more independent clauses, such as in the following examples:

Sentence Structures 4.1 Compound Sentences

In the above examples we can see that the compound sentence (a) has two independent clauses joined with a comma (,) and ‘and’, while the compound sentence (b) has three independent clauses joined with commas, ‘but’ and ‘and’. For compound sentences, there’s grammatically no limit as to how many independent clauses can be conjoined; however, any more than three independent clauses in one sentence tends to become difficult to understand.


3. Join Independent Clauses Correctly

It’s critical that you learn to join your independent clauses correctly when creating compound sentences, otherwise you may be left with ungrammatical run-on sentences, comma splices and sentence fragments. The general (and most commonly used) rule is that every independent clause should be joined with both a comma (,) and a coordinating conjunction (and, so, but, etc.), as was shown in the previous examples. However, there may be times when the writer wishes to show a closer connection between two independent clauses by instead joining them with a only a semi-colon (;), which is perfectly grammatical also.

Sentence Structures 4.2 Compound Clauses with a Semicolon

However, never join two independent clauses with only a comma, as this would be considered an ungrammatical comma splice, which is a type of sentence run-on.

Sentence Structures 4.3 Incorrectly Joined Compound Clauses

4. Avoid General Compounding

One final aspect to watch out for is that you don’t become confused between the general compounding of sentence elements and the conjoining of two or more independent clauses. Such confusion is likely to occur because both structures tend to use coordinating conjunctions such as ‘and’ to conjoin their elements.

Sentence Structures 4.4 General Compounding

Notice in the above sentence that there’s only the one subject ‘I’, generally indicating that there’s only one clause. The two predicates ‘learning about architecture’ and ‘studying […] in English’ in this example and have been compounded, but this sentence is still only simple and not compound.

4 of 8 Lessons Completed


Once you’ve completed all eight lessons about sentence structures, you might also wish to download our beginner, intermediate and advanced worksheets to test your progress or print for your students. These professional PDF worksheets can be easily accessed for only a few Academic Marks.

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