Commas for Parenthesis

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Using Commas for a Parenthesis

Commas can be used to separate a parenthesis from the rest of the sentence. (A parenthesis is additional information that is not essential to the meaning of the sentence, i.e., it could be removed.)

It is also possible to use dashes or parentheses (brackets) to offset a parenthesis. Commas, parentheses, and dashes are types of parenthetical punctuation.

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What is parenthetical punctuation?

When used to offset a parenthesis, commas, dashes, and parentheses (brackets) are called parenthetical punctuation.
  • Commas: While on holiday in London, Simon Schmidt, a fireman from New York, rescued a cat from a tree.
  • Parentheses: While on holiday in London, Simon Schmidt (a fireman from New York) rescued a cat from a tree.
  • Dashes: While on holiday in London, Simon Schmidt — a fireman from New York — rescued a cat from a tree.
Read more about the options for parenthetical punctuation.

What is a parenthesis?

A parenthesis is additional information in a sentence. If a parenthesis is removed, the sentence still makes sense. For example:
  • The defendant, Mr. Michael Evans, sat in silence.
    • ("Mr. Michael Evans" is additional information. This is a parenthesis.)
  • The last owner of the Red Lion, who is my sister's friend, won over 4 million on The National Lottery.
    • (The clause "who is my sister's friend" is additional information. This is a parenthesis.)
When a parenthesis re-describes or re-names a nearby noun, it is known as parenthesis in apposition. In the top example, "Mr. Michael Evans" re-describes "the defendant." It is an example of parenthesis in apposition.

When used mid-sentence, comments such as "however," "therefore," "as a result," and "as far as I am concerned" fall into the category of parenthesis too. These, however, are not offset with parentheses (brackets) but commas and — at a push — dashes.
  • John Winfield, on the other hand, is an experienced jockey.
  • We have really everything in common with America nowadays except, of course, language. (Playwright Oscar Wilde)
Read more about the definition of parenthesis.

Examples of Commas Used as Parenthetical Punctuation

In each example below, the parenthesis is shaded:
  • The second boat in the race, the 6-berth Kontarka, was crewed by local school children.
  • Mr. Tommy Millar, 36, was jailed for robbing his father's grocery store.
  • James, a 23-year-old beggar from Boston, left his 4-million-pound mansion to live on the streets.
  • Last year's pizza-eating champion who works with my brother came in here and ate two loaves of bread in one sitting.
    • (This is wrong because "who works with my brother" should be separated from the remainder of the sentence using one of the types of parenthetical punctuation, e.g., commas.)
  • Critics search for ages for the wrong word, which, to give them credit, they eventually find. (Actor Peter Ustinov)

A Parenthesis Is Not Always Mid-Sentence

A parenthesis is not always mid-sentence. For example:
  • They will be taking Jamie, a young man from London.
    • (When a parenthesis ends a sentence, only one comma (or dash) is needed to offset it. (Obviously, if parentheses (brackets) are used, then both the open bracket and the close bracket are needed.)
When a parenthesis is mid-sentence, you must offset both ends of it; i.e., you cannot use just one comma. For example:

You Must End Your Parenthesis!

  • Mr Tommy Millar, 36 was jailed for robbing his father's grocery store.
  • Critics search for ages for the wrong word, which, to give them credit they eventually find.
These are as wrong as failing to use a closed bracket.
  • Mr Tommy Millar (36 was jailed for robbing his father's grocery store.
    • (A mistake with parentheses (brackets) is extremely rare. It is most often seen with commas.)

Choose Your Parentheses to Assist Your Reader

Although the use of commas as parenthetical punctuation makes for a normal-looking sentence, commas can become confused with other commas in the sentence. For example:
  • Last night, Josie, an escaped wallaby from London Zoo, attacked two young sisters, Rebecca and Josie, which is pure coincidence, Evans, in a bid to steal their crisps.
    • (Although grammatically correct, the writer could have used a mixture of parenthetical punctuation to make the sentence clearer.)
This example with a mix of parenthetical punctuation is easier to read:
  • Last night, Josie (an escaped wallaby from London Zoo) attacked two young sisters – Rebecca and Josie (which is pure coincidence) Evans – in a bid to steal their crisps.
Interactive Exercise
Here are three randomly selected questions from a larger exercise, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

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See Also

Using commas (a summary) Our big commas test A Key Stage 2 (KS 2) test on parenthesis More about your choice of parenthetical punctuation What is a parenthesis? More about parenthetical punctuation Commas after a sentence introductions Commas after a transitional phrase Commas after interjections (yes, no, indeed) Commas before conjunctions (and, or, but) Commas in lists Commas with a long subject Commas with numbers Commas with quotation (speech) marks Commas with the vocative case Commas with Dear, Hello, and Hi