Punctuating Simple and Compound Sentences


Learning grammar is like learning refrigeration repair. At some point you have to learn the names of the parts. One essential piece of grammatical terminology is the clause. A clause has to have at least one subject and one verb. Here’s an example of a clause:

Ron sleeps.

Ron is the subject, and sleeps is the verb. I can throw in lots of other words and still have just one clause: “Ron sleeps at his desk during lectures on grammar.” “Ron” is still the subject, and “sleeps” is still the verb. The groups of words “at his desk,” “during lectures,” and “on grammar” are phrases. A clause can have more than one subject and more than one verb:

Ron and Pam sleep and snore at their desks during lectures on grammar.

“Ron and Pam” are the subjects, and “sleep and snore” are the verbs. It’s still just one clause.

A clause that can stand on its own is called an independent clause. An independent clause by itself is a sentence. “Ron sleeps” is a sentence. So is “Ron and Pam sleep and snore.” One independent clause is a simple sentence. Two independent clauses can be joined to make a compound sentence

Rule One: Two independent clauses can be joined by a coordinating conjunction—for, and, nor, but, or, yet, so. (A handy acronym for coordinating conjunctions is FANBOYS.) When a coordinating conjunction joins two independent clauses, it has to be preceded by a comma:

Ron sleeps at his desk, and Pam listens to the lecture.

Rule Two: Two independent clauses can also be joined by a semicolon (;).

Ron sleeps at his desk; Pam listens to the lecture.

NB: Two independent clauses joined by a semicolon have to be closely related thoughts.  Ron sleeps at his desk  can’t be joined by a semicolon to Pam is taller than her brother.

Rule Three: Two independent clauses cannot be joined by just a comma. This is a sentence fault called a comma splice. Two independent clauses with no punctuation between them is a run-on, another sentence fault:

Ron sleeps at his desk, Pam listens to the lecture. (Comma splice)

Ron sleeps at his desk Pam listens to the lecture. (Run-on)

Two very short independent clauses (fewer than four words) can be joined by a comma:

Man plans, God laughs.

Armed with this terminology and the three rules, insert commas or semicolons where appropriate in the following sentences. You have to decide whether each sentence is simple (one clause) or compound (two clauses).


  1. Our dog Theo loves to go on walks and spray all the trees.
  2. Reuben’s dog Cleo loves to go on walks but she always gets in fights with other dogs.
  3. Our friend Ursula walks Theo every day and feeds our cat.
  4. Theo likes to drink water from toilets Cleo prefers to drink water from bowls.
  5. Cleo and Theo sometimes go on walks together but don’t pay much attention to each other.
  6. Ursula slipped on the ice and hurt her leg so she hasn’t walked Theo this week.
  7. Ursula has cabin fever and is going crazy Theo is very restless and is growing impatient.
  8. Theo sheds a lot so I have to brush him every day.
  9. Our cat Izzy also sheds a lot nobody has ever tried to brush her.
  10. We just bought new furniture and no longer let Izzy and Theo come into the living room.


Answers: 1. No comma or semicolon (simple) 2.  A comma after “walks”(compound) 3.  No comma or semicolon (simple) 4. A semicolon after “toilets” (compound) 5. No comma or semicolon (simple) 6. A comma after “leg”(compound) 7. A semicolon after “crazy” (compound) 8. A comma after “lot” (compound) 9. A semicolon after” lot” (compound) 10. No comma or semicolon (simple)

4 thoughts on “Punctuating Simple and Compound Sentences

  1. A couple of questions:

    1) Clauses are sentences, so why are there two terms for the same thing? Surely it’s not just dependent on how long the clause is?

    2) For some of the clauses above, I would normally add a comma where you don’t:

    #3: Is it “wrong” to put a comma after “day”? Why?
    #5: Is it “wrong” to put a comma after “together”? Why?


    1. At first I mistakenly titled this post “Punctuating Simple and Compound Clauses.” I mean, of course, “Simple and Compound Sentences.

      In #3 and #5 no commas come before the coordinating conjunctions because they are not joining clauses. Both are simple sentences.


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