The comma is the most complicated punctuation mark in the English language. Not only does it have many uses, but it also has many misuses. In The Elements of Style by William Strunk Jr and EB White (Amazon), four punctuation principles were deemed most important and that “they should be so thoroughly mastered that their application becomes second nature.” 

Now,  if you’re ready, grab a pen and notebook, strap yourself in because we are going to quickly go through these 4 important punctuation rules:  

1.  Enclose parenthetical expressions with commas 

Take this example:

The dog that ran away came back with a cat. 

The fact that the dog ran away is extra information. But this information is also essential to the sentence.

It’s this essentialness, or restrictiveness, that determines the role commas play.

A parenthetical expression is a word or phrase that adds to the sentence to give extra information. 

If the information is essential such as in: 

The dog that ran away came back with a cat. 

You may omit the commas. 

However, you can add commas to separate, if the information is nonessential, such as in: 

The dog, hungry for treats, came back with a cat. 

So remember it this way, if the information is essential you may omit the commas, but if the information can be removed without influencing the meaning of the sentence then you should add the commas. 

Another way to put it is to recognize nonrestrictive terms and clauses, as they will often require commas. In the middle of a sentence these nonrestrictive clauses are often preceded by “Which”, “When”, and “Where”: Such as:

The car, which was illegally parked, got towed. 

Nonrestrictive clauses may also appear at the beginning of a sentence:

Parking the car illegally, the man hurried into the store. 

To summarize:

You won’t need commas for a sentence like: The boy is a criminal.  

But you will need one for: My son, Billy, stole my car. 

How are we doing? A little confusing, eh? You’re not alone. This rule for me is one of the most challenging in the entire language because sometimes the importance of the information can feel subjective. 

But don’t feel bogged down by all the commas, Strunk and White give you permission to omit them if the interruption is short. 

If you are to remove the commas, however, don’t remove one but not the other. 

If you are to remove the commas, however don’t remove one but not the other. 

Personally, I always use commas to break up “however”, as well as dates: Saturday, June 4, 2022

2. Place a comma before a conjunction introducing an independent clause. 

A conjunction is a word that connects two separate elements or sentences. Common examples include FANBOYS:

• For
• And
• Nor
• But
• Or
• Yet
• So

And also:

• As (used in relation to Because)
• While (used in relation to events happening at the same time) 

When a conjunction comes before an independent clause (which can serve as a single sentence in itself), a comma is required in front of it. 

The traffic was bad, but the robbers were going to escape no matter what. 

Or

The police chased on foot, for the roads were gridlocked. 

However, with a dependent clause, it gets a little tricky. 

According to Strunk and White: If the clauses in the sentence share the same subject, the subject is only expressed once, and the conjunction is “but” then adding a comma will be useful. 

The robbers found a hiding spot, but forgot to take the money. 

However, if the conjunction is “and” then omitting the comma will be okay as the two interlinking thoughts are closely related. 

The police found the money in the car and decided to keep it for themselves. 

3. Do not join independent clauses with a comma. 

If you have two complete and separate thoughts with their own subject and verb, such as:

WRONG: The monster emerged from the swamp, the terrified campers climbed up the tree. 

Do Not place a comma between them. 

To correct it, you have a few options: 

The first option is breaking it into two sentences and using a period — or an exclamation mark — while capitalizing the first letter of the following sentence: 

The monster emerged from the swap. The terrified campers climbed up the tree.

The monster emerged from the swap! The terrified campers climbed up the tree. 

Alternatively, you can combine the sentences by using a semi-colon or adding a comma and conjunction. 

The monster emerged from the swap; the terrified campers climbed up the tree.

The monster emerged from the swap, so the terrified campers climbed up the tree. 

As you can tell, changing the punctuation mark changes the relationship between the two statements. The better you understand this principle, the better control you’ll have of your writing style. Personally, I’m a comma/conjunction type of guy, but let me know which one you prefer in the comment below. 

4. Do not break sentences in two. 

Simply put, commas cannot replace periods and periods cannot replace commas. A period’s primary function is to separate complete sentences, so when you use it instead of commas, you’ll likely end up with sentence fragments. For example: 

He was a wealthy man. Having earned all his money through buying and trading crypto. 

It should be: 

He was a wealthy man, having earned all his money through buying and trading crypto. 

A complete sentence has a subject and verb, and while the first part can stand as an independent clause, the second half of that sentence is missing the subject. 

An exception to this principle, which I’d recommend using sparingly, is to break the sentence when you want to emphasize a specific word. Such as: 

He punched the wall. Hard. 

There you have it! Those are four of the most important punctuation principles according to Strunk and White. Once you get a hang of them, you will be well on your way to being a proficient writer and editor with another tool in your tool belt. 

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