The construction of a sentence determines if a clause is essential or nonessential. Unlike other mind-boggling aspects of English grammar, the distinction between these is gentle on the mind and easy to remember. We need essential clauses to clarify a sentence. On the other hand, a nonessential clause adds detail the writer might want to include for a number of reasons, but it’s not necessary to improve meaning. In other words: A nonessential clause can often be deleted without changing its sense.
On rewrite, the difference can be capital. Nonessential clauses contribute details, nuances, and color to flesh the narrative style. However, they may also clutter otherwise powerful sentences and render them listless.
Call me, so we are on first-name terms, Ishmael.
We cringed with aesthetic horror as we wrote “so we are on first-name terms.” The clause is cliché, unnecessary and telling. Mr. Melville’s bones would rattle. Many writers would defend such an aberration on the grounds that the sentence “needs” the information. In doing so, they would underestimate the average reader’s imagination and the beauty of showing.
“Call me Ishmael,” besides being one of the most rotund first lines in English literature, already implies what we’ve added. Rather than additional information, the additional clause is redundant.
Before we delve further, it’s important to point out that U.S. grammarians often refer to essential and nonessential clauses as restrictive and nonrestrictive and the British as defining and non-defining. These are different words to name the same classifications.
So then, essential or non-essential. What’s the difference?
When a sentence is vague, an unclear noun—which may or may not be the subject of the sentence—is often the culprit.
The boy ran to join his friends by the pond.
Unless we have disclosed the boy’s identity on previous lines, a reader might frown: which boy? There are many boys in the neighborhood.
The man has landed a leading role in the Pirate’s play.
If we have introduced several men in our tale, trying to determine which man is on his way to stardom may prove difficult.
To help the reader work out which boy or man we’re writing about, we need a helping clause. And that’s the role of essential clauses.
An essential clause is a group of words that adds precision to an ambiguous noun. Check these reworked examples:
The boy who wolfed down his sandwich ran to join his friends by the pond.
Okay, now we know. It’s the boy with the big appetite.
The man who owns a chatty parrot has landed a leading role on the Pirate’s play.
That man? Now we wonder who’s landed the job; the man or the parrot.
These clauses have helped clarify the nouns “boy” and “man” by adding information.
Next we can turn the essential clauses above into nonessential clauses by tweaking the sentences a little:
Timmy, who wolfed down his sandwich, ran to join his friends by the pond.
Mr. Burns, who owns a chatty parrot, has landed a leading role on the Pirate’s play.
In place of indefinite nouns like “boy” or “man” we have specific proper nouns: Timmy and Mr. Burns.
Changing the nature of the nouns has had a deeper effect on those sentences. The clauses are now nonessential. Although the detail in these clauses might be colorful or interesting, it’s not necessary, for we know which boy and which man because they are named. To signal the nonessential nature of these clauses, we have surrounded them with commas to separate them from the rest of the sentence.
A word of warning. Nonessential clauses interrupt the flow of a sentence and can affect the pace because the reader will pause at the information. If the information is not essential for clarity, it should be deleted.
To sustain pace and narrative flow, it pays to remove nonessential clauses. The removed clause can be crafted into a short sentence to follow the original or, if it contains important details, we can rewrite the complete sentence.
The man, who runs the cafeteria, is the only Tutsi in Queens.
The man is the only Tutsi in Queens. He runs the cafeteria.
In many instances, and to control pace, a pair of terser sentences might be more effective than one containing commas.
And another word of caution. Punctuation is not without risks, and writers should exercise great caution, lest they alter the meaning of their sentences with a comma.
The hobo, who leans on a lamppost, will make a killing from churchgoers.
This example, with commas, contains a nonessential clause. It refers to a specific hobo. It tells us his whereabouts, then about his profits.
The hobo who leans on a lamppost will make a killing from churchgoers.
The second example uses an essential clause. Without the commas, the sentence states that any hobo who leans on a lamppost will benefit from the churchgoers’ largesse.
Essential and nonessential clauses
The construction of a sentence determines if a clause is essential or nonessential. Unlike other mind-boggling aspects of English grammar, the distinction between these is gentle on the mind and easy to remember. We need essential clauses to clarify a sentence. On the other hand, a nonessential clause adds detail the writer might want to include for a number of reasons, but it’s not necessary to improve meaning. In other words: A nonessential clause can often be deleted without changing its sense.