Grammar for Academic Writers: Essential Clauses

Whether you are a native or non-native English speaker, you may come across situations where you are unsure where to place commas in a sentence. Today, I’ll cover those phrases where you should not use a comma to surround supporting information—essential clauses—and discuss the difference between these and nonessential clauses. The decision to add a comma in these cases often depends on the meaning of the sentence, so it can require some reflection and detective work.

Here’s an example of an essential clause (bolded for emphasis):

The students who visited the writing center enhanced their confidence.

Here, we have an essential clause because we are explaining a specific group of students. Which students? The ones who visit the writing center.

You might be tempted in this example to use commas instead for something like this:

The students, who visited the writing center, enhanced their confidence.

Here’s where it gets tricky because both of these sentences are grammatically correct—they just have different meaning depending on if we use commas or not.

In the first example we mean specifically that the students who visited the writing center enhanced their confidence. This implies that there are other students who did not visit the writing center. In the second example, we mean that all the students visited the writing center and therefore their visit is not essential information to understanding our meaning—it’s nonessential, meaning we should surround it with commas.

Another way to think of this is if you are considering surrounding a clause with commas, try writing out the sentence without the information in the commas. If that sentences still conveys the meaning you intended, then you have a nonessential clause. However, if the sentence makes sense but doesn’t convey the meaning you intended, then it’s likely an essentialclause and shouldn’t use commas.

An example will be helpful to illustrate this situation.

The assignment due Thursday was very difficult.

Let’s try the comma test:

The assignment, due Thursday, was very difficult à The assignment was very difficult.

So now we have a decision to make: Do we want to emphasize that it’s this specific assignment? In that case, we’ll keep it without commas. But if the date it’s due doesn’t impact the meaning we intend, we’ll add those commas.

Next time you’re wondering about comma placement and essential or nonessential information, consider your meaning and try this simple test!

Note that essential clauses can also be called restrictive clauses, whereas nonessential clauses can be called nonrestrictive clauses. Read more on our grammar page on this topic as well!

Claire Helakoski is a writing instructor at the Walden Writing Center. Claire also co-hosts WriteCast, the Writing Center's podcast. Through these multi-modal avenues, Claire delivers innovative and inspiring writing instruction to Walden students around the world.

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