Grammar Essential and Nonessential Elements, Part II |
The Blue Book of Grammar and Punctuation

Essential and Nonessential Elements, Part II

Here is the rule again, in case you missed it: Essential elements in a sentence should not be enclosed in commas. Nonessential elements in a sentence should be enclosed by commas.

Last time, we applied the rule to clauses. Today we’ll look at essential and nonessential phrases (a phrase is two or more related words with no subject and verb).

Let’s start with this sentence: The guy seated next to me wouldn’t stop talking. There are no commas because seated next to me is an essential phrase. It identifies which “guy” we mean. Without it we’d have only The guy wouldn’t stop talking, which doesn’t tell us much.

But consider this: Ezra Blung, the guy seated next to me, wouldn’t stop talking. Because we now know the man’s name, the guy seated next to me becomes nonessential. As the commas signify, the phrase contains supplementary information, and the sentence would have the same meaning without it.

Commas are easy for some to overlook, but an omitted or out-of-place comma can change a sentence’s meaning. Here is an example: Complete the job, as directed. The comma after job tells us that the phrase as directed is nonessential. The sentence says that you have been directed to do a job, and implies that how you do it is up to you. But what if we took out the comma: Complete the job as directed. Now as directed is essential, and the sentence is saying something more severe: Do the work, and make sure you do it the way you were told to do it.

Remember that essential and nonessential are technical terms. Some authorities prefer restrictive and nonrestrictive, perhaps to avoid the sort of confusion that may result from analyzing a sentence like this: A comma, which never ends a sentence, signals a pause.

In that example, which never ends a sentence is nonessential, and the crux of the sentence is, A comma signals a pause. That is true, but a period also signals a pause. Perhaps the key difference between commas and periods is that a comma never ends a sentence.

So how could such an essential fact be termed “nonessential” in a sentence that describes a comma? It’s because we are using grammatical terminology: nonessential refers to sentence structure only.

Information essential to human understanding is often found in phrases and clauses that are technically nonessential, as seen in the comma sentence above. But that sentence would be improved by making its less important fact nonessential: A comma, which signals a pause, never ends a sentence.

Memo to fledgling writers: If you find that you’ve disclosed an essential fact in a technically nonessential phrase or clause, you may want to write a new sentence.


Pop Quiz

Identify and punctuate (if needed) the italicized groups of words below. Are they clauses or phrases? Are they essential or nonessential? Answers are below.

1. People demanding special treatment make me angry.
2. His brother who is a health nut runs five miles a day.
3. A friend of mine who lives in Boston loves the seafood there.
4. Alan Lomax always fascinated by roots music first recorded the bluesman Lead Belly.


Pop Quiz Answers

1. People demanding special treatment make me angry. (essential phrase, no punctuation)
2. His brother, who is a health nut, runs five miles a day. (nonessential clause, commas added)
3. A friend of mine who lives in Boston loves the seafood there. (essential clause, no punctuation)
4. Alan Lomax, always fascinated by roots music, first recorded the bluesman Lead Belly. (nonessential phrase, commas added)

If the article or the existing discussions do not address a thought or question you have on the subject, please use the "Comment" box at the bottom of this page.

18 responses to “Essential and Nonessential Elements, Part II”

  1. Ravi Bedi says:

    Your examples:

    2. His brother, who is a health nut, runs five miles a day. (nonessential clause, commas added)
    3. A friend of mine who lives in Boston loves the seafood there. (essential clause, no punctuation)

    Using the same principle I find nothing wrong with the following:

    A friend of mine, who lives in Boston, loves the seafood there.

    • The phrase “who lives in Boston” identifies which “friend” you are talking about (assuming that you have more than one friend). It also identifies the word “there” in the sentence. Therefore, it is essential and requires no commas.

  2. Tony says:

    Thank you. Does the use of brackets to distinguish non-essential elements from essential elements accomplish the same as commas ?

    • Brackets are only used in special cases. Brackets, as opposed to parentheses, are used exclusively within quoted material. They are added by someone other than the original speaker in the quote to explain the quotation. Example:

      “Bill shook hands with [his son] Al.”

  3. Ravi Bedi says:

    How about this:

    His brother, a health nut, runs five miles a day.
    Or this:

    A friend of mine in Boston loves the seafood there.

  4. Lois Robinson says:

    I am a court reporter and am proofreading another reporter’s transcripts. Looking for some rules or guidance to support putting commas around phrases like “let’s say”, “I mean”, and “then” when it means “in that instance. For example:

    I mean, I thought you were coming to work today.
    What kind of things did you enjoy doing during, let’s say, the school year.

    He doesn’t think commas are needed. I strongly disagree. What’s your take on it?

    • Our Rule 4b of Commas says, “Use commas to set off expressions that interrupt the sentence flow (nevertheless, after all, by the way, on the other hand, however, etc.).” Your examples fall under this rule. Therefore, commas are advised.

  5. Jen says:

    Poking fun at this trend, the creators of a popular comedy show IFC’s Portlandia changed their early theme song “The Dream of the ’90s is Alive in Portland.” Is IFC’s Portlandia essential or nonessential? If it’s “a” instead of “the” popular comedy show, shouldn’t it be essential because we don’t know which comedy show the author is talking about? Or is it nonessential because the sentence is okay without the information?

  6. KW says:

    Can there be a nonessential inside a nonessential like “bob, the son of a wealthy doctor, adam, went to college for a degree in medicine

    • The point in question doesn’t apply to essential and nonessential elements, but rather to appositives, which are nouns or noun substitutes set beside other nouns or noun substitutes to identify
      or explain them:
      Bob, the son of a wealthy doctor [appositive for Bob], Adam [appositive for doctor], went to college for a degree in medicine. Grammatically, this is accurate and acceptable; at the same time, without having the wider context to consider, we wonder if the sentence would benefit from further clarity and identification by including a last name – e.g., “Bob, the son of a wealthy doctor, Adam Johnson, went to college for a degree in medicine.” If Bob’s last name is already known, then this would not be needed.

  7. Susi says:

    I have a question. If I have a nonessential clause which contains a comma, how should I punctuate around it?

    My good friend Eve, who lives in Paris, France, sent me a guide book in preparation for my trip.

  8. Kathy says:

    I’m trying to clarify the relationship of appositives to essential/nonessential (restrictive/nonrestrictive) elements. Are appositives considered a subset that are written as a noun phrase? If not, what is the difference? Thanks!

    • By definition, an appositive is a noun or a noun substitute set beside another noun or noun substitute and identifying or explaining it. An appositive can be either restrictive or nonrestrictive.

      Restrictive: His daughter (noun) Sarah (appositive) is a talented singer. (He has more than one daughter; omitting commas communicates this and ensures clarity.)

      Nonrestrictive: I know Paul (noun), an astute thinker (appositive) and a witty raconteur (appositive). (The noun phrases set off by the comma are descriptive of Paul and not essential to clarity.)

      Nonrestrictive: I doubt that Paul (noun), an astute thinker (appositive), would behave so rashly. (The noun phrase set off by commas is descriptive of Paul and not essential to clarity.)

      Also see our post Commas with Appositives for more information.

  9. Becky Stephens says:

    If a prepositional phrase ends the sentence, do you put a comma before it if it’s nonessential? It seems all I ever see for examples online for nonessential phrases pertain to introductory prepositional phrases or when the prepositional phrase is embedded in the middle of the sentence. Sometimes I find it confusing. Also, will moving around the nonessential prepositional phrase ending the sentence tell me if it is nonessential, like other phrases? Thank you for helping.

    • says:

      We do not usually identify prepositional phrases as essential or nonessential. Punctuation can help clarify what they are modifying sometimes, but they are not essential or nonessential in the way that relative clauses can be.

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