Essential & Nonessential Clauses

Types of clauses We’ve already discussed both Dependent and Independent Clauses, and we already know that a clause is a group of related words that contain both a subject and a verb (predicate). But there is yet another classification of clauses: Essential and Non-essential.

The essential Clause An essential clause is a relative clause that limits a general, ambiguous noun. The essential clause tells the reader which one of many the writer means.

Example of Essential clause Apples that are green are not sweet. That are green is an essential clause because it completes the meaning of the sentence. These clauses are called restrictive clauses because they restrict the possible range of what is being talked about. In this case, the apples must be green.

The man who ordered another double anchovy pizza claims to have a pet dolphin in his backyard pool. Which man among the billions of human males on the planet? The one who ordered the double anchovy pizza!

Freddie hopes to return to the city where he met a woman with haunting green eyes. Which of the many cities on the planet? The one where Freddie met a memorable woman!

The essential clause The student who needs an A on the final exam is copying statistics formulae on her bare ankle. Which of the many students in the class? The one who needs an A on the test!

Nonessential Clauses Non-essential clauses (also known as non-restrictive clauses) appear after the sentence and add extra, unnecessary information.

Golden Delicious apples, which are yellow, are sweet Golden Delicious apples, which are yellow, are sweet. Which are yellow is a non-essential clause because it defines the nature of the apples, not the sweetness; it is unnecessary to complete the sentence. These clauses are called non-restrictive because they place no limit on the possible range of what is being talked about. In this case, Golden Delicious apples are sweet, and they just happen to be yellow in color as well.

Note that the exact same clauses above—in sentences with minor alterations—can become nonessential. Read these versions: Mr. Hall, who ordered another double anchovy pizza, claims to have a pet dolphin in his backyard pool. Freddie hopes to return to Cairo, where he met a woman with haunting green eyes. Veronica, who needs an A on the final exam, is copying statistics formulae on her bare ankle.

In place of ambiguous nouns like man, city, and student, we now have Mr. Hall, Cairo, and Veronica, specific proper nouns. The information in the relative clauses might be interesting, but it's not necessary, for we already know which man, which city, and which student. Because these clauses are now nonessential, they require commas to separate them from the rest of the sentence.

A proper noun won't always signal that the relative clause is nonessential. In a passage of more than one sentence, you will sometimes find such a well-defined common noun that the relative clause is a mere accessory.

Read this example: As we sped through the neighborhood, we spotted crows eating French fries tossed on the road. They did not fly to a tree as we expected. The birds, which never showed fear of the vehicle, watched as we swerved around them.

The relative clause which never showed fear of the vehicle is nonessential since we know which birds. Thus the clause requires commas.

Punctuate essential clauses correctly. Since an essential clause provides necessary limits on the vague noun it describes, use no punctuation to connect it. The car that Madeline purchased from a newspaper ad belches black smoke whenever she accelerates. The rats are nesting in the closet where Grandma hides her money. The waiter who served the salad did not notice the caterpillar nibbling a lettuce leaf.

When the clause becomes decorative rather than defining—or nonessential—you will then need to separate it with commas: The ancient Buick, which Madeline purchased from a newspaper ad, belches black smoke whenever she accelerates. The rats are nesting in the master bedroom closet, where Grandma hides her money. Javier, who served the salad, did not notice the caterpillar nibbling a lettuce leaf.

Punctuation for essential and non-essential clauses is simple Punctuation for essential and non-essential clauses is simple. If it is essential, it takes no punctuation. It if is non-essential, put commas around it. ALWAYS!

Let’s go back to that Golden Delicious apple sentence: Golden Delicious apples, which are yellow, are sweet. If you notice, the clause (in bold) is set off by commas. What happens if you remove those commas? The sentence is still correct, but now for a Golden Delicious apple to be sweet, it must be yellow. Taking out those commas made the clause essential to the meaning of the sentence.

Think of it this way: When the commas are there, the clause describes  the color of the apples. When the commas are gone, the clause limits the range of sweet Golden Delicious apples to only the yellow ones.

Common Errors Most people make the mistake of punctuating essential and non-essential clauses incorrectly. The simple test is to take out the clause: If the sentence makes sense AND does not change meaning, add commas. If the sentence makes sense AND changes meaning, leave the commas out.

Most people make the mistake of only seeing whether the sentence still makes sense, but the key is meaning.

One thing that may help you identify essential and non-essential clauses is the That/Which Test. Essential clauses use that, non-essential clauses use which.

NOTE: Clauses don’t have to use one of those two words, but if you ever see a clause that starts with that or which, you can immediately identify it as essential and non-essential respectively. By the way, if you’ve ever heard an editor or English teacher talk about going on a which hunt, this is what they are talking about. They are making sure that the writer didn’t mix up using that for which and vice-versa. Many writers make the mistake of confusing the words. Oddly enough, editors and teachers make the same mistake too, but their error is more often because they completely eliminate one or the other which is, of course, incorrect.

Practice For each of the following questions, you could make the argument that the clause is either essential or non-essential. First, identify the clause and then identify how it changes meaning if the clause is essential or non-essential. I’ve given you my answer for the first one. I’ve purposefully left out the commas.

The computer that is on the table will be thrown away. My Answer: The clause is that is on the table. If you make it essential (no commas), it specifically identifies which computer is to be thrown away. If it is non-essential (commas), you would have to assume that there is only one computer and that both the speaker and the hearer know which computer is being talked about. In this case, it makes a lot more sense to leave the clause as essential, but you could make it non-essential depending on the context.

The car that I bought yesterday is missing. My new car which I bought yesterday is missing. The lake that we visited last year is now severely polluted. Our teacher who wrote the textbook is Mr. Allen.