Commas, Commas, Everywhere!

Comma Before So

Should there always be a comma before the word so? No. It really depends on where and how it is used in the sentence. In the middle of a sentence? Hmm… that depends. If it is used as a coordinating conjunction (i.e., before an independent clause), yes. If it is used before a dependent clause (i.e., a phrase that cannot be a complete sentence by itself), no. Do not use a comma in such instances.

• Karen always grabbed the high-priority files, so she was added to the special priority team.
• I grab the high-priority files so I can get the higher pay rate.

The Oxford Comma (a.k.a. the Serial Comma)

When you have a list of three or more elements, use commas to separate them. The Oxford comma (also known as the serial comma) is the comma before the conjunction and the final element in the series.

• Halloween and Thanksgiving are my favorite holidays because they are in the fall.
  • There are only two elements, so no comma is needed. (Just like with two subjects).

• Easter, Halloween, and Christmas are my favorite holidays because of all the candy.
  • Here we have three elements, so we use commas to separate them from each other (but don't put a comma after the last item because we do not want to separate the subjects from the verb, are).

• Kelly likes to run and swim.
  • Only two elements here, so there is no comma needed.

• Kelly entered a triathlon where she will be running, swimming, and bicycling.
  • Three elements, so we use commas to separate them from each other.

Note that if the list items are separated by a conjunction, we do not use commas (except for unusual circumstances where a comma would aid clarity).

• I do not like carrots or corn or peas.
• I love ice cream and cake and cookies and candy.

Multiple Adjectives

But what about multiple adjectives? If the adjectives modify the noun to an equal degree, separate them with commas. If they do not modify the noun to an equal degree, do not use a comma. To determine whether the adjectives are modifying the noun equally, try switching the order of the adjectives. If it still sounds natural, they are equal and require a comma.

• She was expecting a harsh verbal warning for her terrible mistake.
  • She was expecting a verbal harsh warning for her terrible mistake. ← No, that doesn't sound right, so no comma needed. She was expecting a harsh verbal warning for her terrible mistake.

• Thomas was excited about the fun, new project.
  • Thomas was excited about the new, fun project. ← Yep. They can be switched, so a comma would be correct. Thomas was excited about the fun, new project.

Restrictive Clauses

Commas with restrictive clauses, as opposed to nonrestrictive, add necessary information for the understanding of the phrase or word it is modifying. They are often introduced by that or who and should never be offset by commas.

• The style guide that she was referring to was updated yesterday.
• The style guide was updated yesterday. → Removed, and although the sentence still makes sense, it is lacking detail that would help the reader understand exactly which style guide was updated.

• The man who lives next door has gone on a three-month holiday.
  • The man has gone on a three-month holiday. → Removed, and although this is still a complete sentence, you can easily see that it is lacking the necessary detail to help the reader understand which man went on holiday.

Direct Addresses and Appositives

Direct Address

Speaking of the man who lives next door, let's talk about direct addresses and appositives. An appositive is a word or phrase that provides additional information that helps to distinguish it in some way. Direct address is when you speak to someone specifically:

• You, Susan, may find this to be interesting.
• I would not have been able to complete the project without your help, Tom.
• Captain, I need you to help me for a moment. (Note that when you call someone by their title only, in effect, it replaces their name.)

Also note: if you were to remove the names (Susan, Tom, and Captain), the sentences still make sense; however, it provides distinguishing information about to whom "you" is referring.

Nonessential Appositives

Nonessential appositives provide additional information that can be removed easily:

• My next-door neighbor, Bob, has gone on a three-month holiday.
• My bedroom, the largest in the house, is the coldest room in the winter and warmest room in the summer.

Note: An appositive's placement within the sentence does not matter. If the appositive begins the sentence, it is followed by a comma. If it is in the middle of the sentence, a pair of offsetting commas are required. If it ends the sentence, it is preceded by a comma. (See the Direct Address examples for all three scenarios).

Comma Before Because?

The comma before because conundrum: Do I put one before because? Yes and no… Because is a subordinating conjunction. A what? A subordinating conjunction. Again, you can read more about them in Subordinate Clauses.

Although it is a subordinating conjunction, because introduces a "clause of purpose" answering the understood question of, "Why?" Generally, there should be no comma to separate the two.

No → Every year, Sarah goes to Florida for vacation, because she loves the beach.
Yes → Every year, Sarah goes to Florida for vacation because she loves the beach.

No → Liz decorated the baby's room in blue, because she thought she was having a boy.
Yes → Liz decorated the baby's room in blue because she thought she was having a boy.

Words or Phrases Added to the Beginning

Introductory Clauses

Introductory clauses are dependent phrases that set the stage for the main action of the sentence. They can include prepositional phrases, appositive phrases, participial phrases, infinitive phrases, and absolute phrases. A comma is needed after the introductory phrase.

• To do well, one must practice.
• Shining brightly, the stars seemed magical.
• After the adjustment, your pay will be substantially higher.

Sometimes, it can be just a singular word. These usually create continuity from the previous statement.

• The staff was getting more and more upset. Meanwhile, the manager was trying to think of ways to resolve the issues.
• Then, the staff decided to be proactive and get screenshots of the technical glitches that were plaguing them.
• Finally, the manager decided to call tech support.

Words Added to the Middle or End

Does Too Need a Comma Too?

When the word too is used to mean also, additionally, besides, etc. and is used as an interrupter (see Nonrestrictive Clauses), it is offset with commas.

• I, too, would like to go see that movie.
• Sarah felt like she, too, was lost in the fray.

When added to the end of the sentence, well, it is debatable and a matter of preference. The Chicago Manual of Style states that one is only needed to note an abrupt shift in thought (meaning as in interrupter and not at the end).

• I like scary movies, but I like romantic ones too.

If I said that (the example above ^^) while discussing different genres of movies, no comma is necessary. However, if I wanted to add emphasis, a comma could be added. It's a judgment call.

Speaker 1: I like romantic movies.
Speaker 2: I like romantic movies, too.

In this example, emphasis is added to show equality between the speakers and that Speaker 1 is not the only one that likes romantic movies.

No comma is needed when it is used to mean excessively, to a higher degree, very, etc.

• Is there such a thing as too much chocolate?
• Jim speaks way too fast.