The Subjective View of Commas

“Let’s eat, Grandpa!”

“Let’s eat Grandpa.”

These sentences are iconic examples of why commas are important. One, simple comma changed the entire meaning of the sentence. Sentences like the ones above are used to show just how important commas (and grammar rules in general) are. However, are all commas really necessary?

As someone who absolutely adores commas, I’ve realized the answer to this question is “No.” Not all commas are necessary. Commas are subjective, not objective. This phenomenon is what makes commas so hard to use.

Sentences with “that” or “which” show just how hard it is to figure out if a comma is necessary or not. The following sentences only have one minor difference. One uses “that,” and one uses “which.” Can you tell which one is correct?

Grab my wallet, which is in my purse.

Grab my wallet that is in my purse.

The answer to this question, surprisingly enough, is both sentences are correct depending on the context. In the first case, the writer assumes the reader already knows where the wallet is. “Which” signifies a non-essential element to a sentence, so the last part of the sentence, “which is in my purse,” can be taken out without removing meaning to the sentence.

In contrast, the writer of the second sentence assumes the reader doesn’t know where the wallet is. The word “that” shows the following information is essential for the reader. If the last part of the sentence, “that is in my purse,” is left out, readers might not have the information they need to accomplish their task.

Quick Guide to Essential and Non-Essential Phrases
A quick and easy way to decide if something is essential or not is to take the part of the sentence out. Does the sentence still make sense without the extra information? Then the phrase is non-essential and often uses a comma and “which” to show that it’s just extra information. Does the reader ask “so what?” or expects more information? Then the phrase is essential and “that” is used without a comma.

It’s important to remember as the author, you are the one who controls the commas. If you can justify why a phrase is essential or non-essential, then you are correct! It’s your writing, so own it! You control commas; commas don’t control you.