Grammar Tips: Understanding the Comma

Nothing gets us in trouble more as a writer than misusing punctuation. A misplaced comma can often change the meaning of what we are saying and confuse our readers. To help you understand the basic rules, I am going to keep the sample sentences very basic.

First rule: Any part of a sentence that can be deleted without changing the basic meaning of the sentence should have commas before and after that word, clause, or phrase.

Example: Oslo, who is my smallest dog, is learning how to sit. Identify the core sentence: Oslo is learning how to sit. The fact that he is my smallest dog is a clause that can be deleted without changing that core sentence. This additional information is just a bonus for the reader. The clause needs to be separated by commas.

If the wording being removed changes the meaning of the sentence, no commas are needed.

Example: Dogs who are afraid of water wouldn’t like to swim in my lake. No commas should be put around who are afraid of water because that is key to the sentence. Without that information, we would only have this: Dogs wouldn’t like to swim in my lake. That isn’t true, however. Lots of dogs do swim in lakes—just not dogs who are afraid of water.

We could change the sentence, though, to give a specific example (and a clause which needs commas: My friend’s dog, who is afraid of water, doesn’t like to ride in boats on my lake. The core sentence is true without the clause about water: My friend’s dog doesn’t like to ride in boats on my lake.

Note for ACT test takers: clauses that start with “that” don’t take a comma; clauses that start with “which” take commas.

Example: Pocket calendars, which can be very difficult to read without glasses, were handed out to students. Calendars that fit easily into coat pockets are too small for me to read.

Note: There is an exception to this rule, though. Pronouns that are used for emphasis are not separated by commas.

Example: The gold medal winner himself came to our soccer game. I myself was surprised.

Second rule: Interruptions/interjections in a sentence need to be set apart by a comma. Anything that breaks the flow of the core sentence could be deleted without changing the meaning.

Example:        However, I still went to the library.

                        I still went to the library, however.

                        I, however, still went to the library.

Third rule: Introductory words, phrases, or clauses should be set apart with a comma. This introduction to a sentence could be the name of a person being addressed or could be a dependent clause giving the reader additional information. Any opening clause or phrase needs a comma after it.

Examples:      Even though I missed the previews, I still arrived in time to see the movie.

                        Megan, are you coming to practice Tuesday?

                        When I’m camping, I like to drink hot cocoa.

                        As unusual as it sounds, we like to hike in really cold weather.

Fourth rule: Commas are used to connect independent clauses (that could stand alone) if they are combined into one sentence using FANBOYS (for, and, nor, but, or, yet, so). These coordinating conjunctions require a comma to be placed before them.

Example:        I wanted to eat pizza for lunch, but my brother ate it all before I got home.

                        I’m saving up for my first car, so I applied for the job at Trader Joe’s.

                        My family bought new bikes, and we are going riding together this weekend.

Notice that these are all independent clauses. They could each stand alone without the conjunctions:

                        I wanted to drink pizza for lunch. My brother ate it all before I got home.

                        I am saving up for my first car. I applied for the job at Trader Joe’s.

                        My family bought new bikes. We are going to ride together this weekend.

Note: “So” can really be a tricky conjunction. If the clause with it is necessary for the meaning of the sentence, no comma is used.

Example: I woke up early so I could go fishing with my friends. (If you could read this as “so that,” no comma is needed. You are telling someone why you woke up early. If you could use the word “therefore” instead of “so,” you use as comma. See the example above.)

Fifth rule: Use commas to separate items in a list.

Example:        I bought sugar, eggs, and flour to bake my desserts.

                        Jenni, August, Paul, and Sarah are coming to my birthday dinner.

                        I am going to do my homework, eat dinner, and watch a movie.

The ACT follows the Oxford comma rule. A comma is used before the “and” preceding the last item in the list.

If multiple adjectives come before a noun and the order that they are listed in doesn’t matter, you need to separate them with a comma.

Example:        I want a green, leafy bush for the front flower bed.

                        I adopted a young, energetic puppy.

If the order matters for descriptive words, no comma is needed.

Example: My first soccer coach played in the Olympics. (First and soccer are both descriptive words. However, it would be incorrect to say: My soccer first coach played in the Olympics.)