Commas for Parenthesis

by Craig Shrives
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Using Commas for a Parenthesis

Commas are used in pairs to mark a parenthesis in a sentence. In each examples on this page, the parenthesis is highlighted.
  • Buzz Aldrin, original name Edwin Eugene Aldrin, was the second person to set foot on the Moon. correct tick
  • Venus, unlike the other planets in our solar system, spins clockwise. correct tick
What is a parenthesis? A parenthesis is additional information that is not essential to the meaning of the sentence, i.e., it could be removed.

Commas are not the only way to mark a parenthesis. It is also possible to use dashes or round brackets (also called "parentheses") to show a parenthesis. Commas, round brackets, and dashes are types of parenthetical punctuation.

What Is Parenthetical Punctuation?

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

More about the Term "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. correct tick
  • We have really everything in common with America nowadays except, of course, language. correct tick (Playwright Oscar Wilde)
Read more about the definition of parenthesis.

More 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. correct tick
  • Mr. Tommy Millar, 36, was jailed for robbing his father's grocery store. correct tick
  • James, a 23-year-old beggar from Boston, left his 4-million-pound mansion to live on the streets. correct tick
  • Last year's pizza-eating champion who works with my brother came in here and ate two loaves of bread in one sitting. wrong cross
  • (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. correct tick (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. correct tick
  • (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.)

You Must End Your Parenthesis!

When a parenthesis is mid-sentence, you must mark both ends of it; i.e., you cannot use just one comma. For example:
  • Mr Tommy Millar, 36 was jailed for robbing his father's grocery store. wrong cross
  • Critics search for ages for the wrong word, which, to give them credit they eventually find. wrong cross
These are as wrong as failing to use a closed bracket.
  • Mr Tommy Millar (36 was jailed for robbing his father's grocery store. wrong cross
  • (A mistake with parentheses (brackets) is extremely rare. It is most often seen with commas.)

Choose Parenthetical Punctuation That Assists the 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.

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