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Essential vs. Non-essential Information

Essential clauses or phrases define or identify without commas.

Commas are not used with phrases that define.
The tornado that tore down my big tree struck at night.

Non-essential clauses or phrases introduce or explain.

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Tornadoes, which can strike day or night, can destroy entire towns.

Commas separate introductory clauses/phrases, explanatory clauses/phrases, or nonrestrictive clauses/phrases from the rest of the sentence.

The information may be essential to the story, but it is not essential to the sentence.

An introductory clause usually adds information as to when or where or why, but it is not necessary for the sentence itself. It should be separated by a comma.

Examples:

  • The next day
  • On May 3, 1842
  • In Denver
  • At the ranch
  • To avoid suspicion
  • Trying to hide
  • When he came, the boy confessed to the crime.

An explanatory phrase/clause explains the word before it but does not define it. Commas around it indicate that the sentence conveys its meaning without the clause or phrase. The information in the phrase or clause is incidental to the sentence.

Examples:

  • Tom, who confessed to the crime, was my neighbor.
    • The sentence is “Tom was my neighbor.”
  • The illegal entry into my house, the third burglary in a row, surprised me, the president of our neighborhood watch.
    • The sentence is “The illegal entry into my house surprised me.”
    • Non-essential information
      • the third burglary in a row
      • the president of our neighborhood watch
  • The chief of police, also in our neighborhood, caught him in the act.
    • The sentence is “The chief of police caught him in the act.
    • Non-essential information
      • also in our neighborhood

A restrictive phrase/clause restricts the word before it to a specific one, defining it. Do NOT set it off with commas.

When “such as” offers essential information, it is NOT followed by a comma.

Example of restrictive:

  • The boy who confessed to the crime owns a BMW.
    • subject = “boy”
    • “who confessed to the crime” identifies/defines which boy owns the BMW
  • The items that were stolen were never recovered.
    • subject = “items”
    • “that were stolen” identifies/defines which items were never recovered
  • The moon on the nights of the burglaries was only a sliver.
    • subject = “moon”
    • “on the nights of the burglaries” identifies when it was only a sliver

The key to surrounding the phrase/clause with commas is to determine if the phrase/clause is essential to the meaning of the sentence.

Examples of restrictive, introductory, and explanatory:

  • R: The planet that is the largest in our system is Jupiter.
    • (Restrictive phrase, defines which planet)
  • I: As the largest planet in our system, Jupiter is surrounded by dust rings.
    • (Introductory phrase = “as the largest planet in our system, set off with a comma)
  • E: Jupiter, the largest planet, is surrounded by rings, mostly formed of dust.
    • (Explanatory phrase =” the largest planet,” surrounded by commas)
  • E: Mrs. C. encouraged her students to study specific punctuation marks, namely, commas.
    • (Explanatory phrase= “namely,” surrounded by commas)
  • R: Horses such as thoroughbreds and Hanoverians tend to be more high-spirited than horses such as Quarter Horses or Morgans.
    • (Restrictive phrase = “such as.” Leaving out the “such as” examples leaves the sentence as “Horses tend to be more high-spirited than horses. That does not make sense. No commas)
  • I: However, the police arrived three minutes after the alarm sounded.
    • (Introductory phrase = “however,” comma before independent clause)
  • E: The police, informed of the activity, arrived three minutes after the alarm sounded.
    • (Explanatory phrase = “informed of the activity,” surrounded by commas)
  • R: The police who were informed of the activity arrived three minutes after the alarm sounded.
    • (Restrictive clause. Only the police who had been informed of the activity arrived)
  • I: In the meantime, the thieves gathered as much as they could.
    • (Introductory phrase = “in the meantime,” set off with a comma)
  • E: The thieves, wearing green masks, gathered as much as they could.
    • (Explanatory phrase = “wearing green masks,” surrounded by commas. With commas, all the thieves were wearing green masks.)

Notice that the following two sentences without commas mean the same, but not the same as the sentence with the commas.

  • R: The thieves who were wearing green masks gathered as much as they could.
    • (Restrictive clause, indicating which thieves were gathering loot while the others stood around and watched, no commas)
  • R: The thieves wearing green masks gathered as much as they could.
    • (Restrictive phrase, indicating which thieves were gathering loot while the others stood around and watched, no commas)

Phrases such as “for example,” “that is,” “namely,” etc. should be surrounded by commas as explanatory.

Examples:

  • E: Mrs. C. encouraged her students to study specific punctuation marks, namely, commas.
    • (Explanatory phrase = “namely,” not essential to the sentence to know which specific punctuation marks the students should study)
  • E: Trenton made several punctuation errors, for example, combining independent clauses with a simple comma.
    • (Explanatory phrase= “for example,” not essential to the sentence to know which specific errors he made)
  • E: Whenever we went to town, we went to the post office, that is, on weekdays when it was open.
    • (Explanatory phrase = “that is,” not critical to the sentence)

This is tricky!

When a non-essential clause follows a FANBOYS, do not put a comma before the non-essential clause (after the FANBOYS).

Examples:

  • He had enough money, but of course, time was too short.
    • (Normally, “of course,” would be set off by commas before and after, but it follows a FANBOYS)
  • The cookie was soft, and what she liked best, it had chocolate chips.
    • (Normally, “what she liked best,” would be set off by commas before and after, but it follows a FANBOYS)
  • Writing sample sentences seems easy, yet to make them interesting, some of them should be funny.
    • (Normally, “to make them interesting,” would be set off by commas before and after, but it follows a FANBOYS)

Photos by Mick Haupt on unsplash, NOAA on unsplash.


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