Essential Vs. Nonessential Sentence Elements

Purdue University’s Online Writing Lab (OWL) offers in-depth guides to all things English. Whether it is APA citation or grammar and punctuation rules, all students should use it as a place of reference to improve their confidence as an English student. Within the section on punctuation, the Purdue OWL has a detailed section on comma usage rules. The first two rules are imperative for every English writer to have down.
-       The first rule states that one should use a comma when combining two complete sentences with a coordinating conjunction (for, and, nor, but, or, yet, so). E.g., The team played hard, but they lost.
-       The second rule states that one should use a comma to separate introductory clauses and phrases from the main clause of a sentence, like beginning a sentence with a subordinating conjunction (because, although, when, unless, before, after, if). E.g., If the team wins this game, they will be in the Final Four.

But the third and fourth rules are a little bit trickier than the first two. They state rules dealing with essential and nonessential elements of a sentence. Often times, I hear students ask what exactly these are and how to identify them. This guide will help you recognize these elements to avoid comma errors in your writing.

The overall message is this: If it is essential one does not need commas; but if it is nonessential, one does need commas.

Many times, writers couch clauses (word groups containing a subject and verb) within other clauses to modify a noun or pronoun. These are called adjective clauses. Let’s take a look at an example:


The woman who won the award last night thanked her parents for support.
[subject]           [adjective clause]                              [verb]

Dogs that are not properly trained can cause harm to furniture.
[subject]           [adjective clause]               [verb]

Ohio State, which won its last three games, will play for the championship tonight.
[subject]           [adjective clause]                                 [verb]


These adjective phrases often restrict the subject; that is, they define the subject in more detail. In the first example, it’s not just any woman but the one who won the award last night. In the second example, it is not just any dog but specifically dogs that are not properly trained.

Commas come into play when deciding whether these adjective clauses are essential or nonessential. With these three examples, try covering up the adjective clauses. Does the sentence still keep the same meaning? Is the adjective phrase just a small fact or is it essential to the overall meaning? In the last example, the fact that Ohio State has won its last three games does not change the fact that it will play for the championship; rather, this is just a side note and is therefore couched in commas. The word that signifies an essential element; the word which signifies a nonessential element.

-       Necessary to retain the meaning of the sentence.
-       Covering it up changes the message conveyed.
-       One does not need to place commas around it.
-       That

-       Acts as more of a side note rather than essential information.
-       If omitted, it does not affect the main clause of the sentence.
-       One must place commas around it.
-       Which

Stay tuned for another comma-related post on participles.
Happy Writing!
-Pete Talbert

Works Cited

Purdue Online Writing Lab. “Extended Rules for Using Commas.” 7 February 2012. Web. 12 March 2012.

Reid, Stephen. “Phrases and Clauses.” The Prentice Hall Guide for College Writers. 8th ed. Upper Saddle River, NJ: Pearson. 2008. Print.

3 Responses to “Essential Vs. Nonessential Sentence Elements”

  1. Writing Center » Participles & Participial Phrases | Your DCTC News Source : Dakota County Technical College Says:

    [...] rule, we need commas with participial phrases because they are almost always nonessential (see the last post). If we begin with a participial phrase, we need a comma before the main clause starts. If a [...]

  2. Grayce Carlee Says:

    Terrific article. I had been checking frequently your blog and I am impressed! Very useful information.

  3. Glayds Chrysler Says:

    :) Props on the website.