What Is Parenthesis?

A parenthesis is a word, phrase, or clause inserted into a sentence as an explanation or afterthought. When a parenthesis is removed, the surrounding text is still grammatically sound.

A parenthesis is usually offset with parentheses (i.e., round brackets), commas, or dashes. These are called parenthetical punctuation marks.

A parenthesis is sometimes called an "interrupter" as it interrupts the flow of text.

Table of Contents

  • Examples of Parenthesis
  • Parenthesis in Apposition
  • Why Parenthesis Is Important
  • Test Time!
parenthesis examples

Examples of Parenthesis

Here are some examples of parenthesis (shaded):
Parenthesis Offset with Parentheses (Brackets)
  • Andrew Jacklin (last year's losing finalist) is expected to win this heat.
  • The whole aim of practical politics is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins, all of them imaginary. (Journalist HL Mencken)
When parentheses (round brackets) are used to offset a parenthesis, the parenthesis is easily seen. However, some writers feel that parentheses can make formal texts look unorganized.
Parenthesis Offset with Commas
  • Paul, on the other hand, is considered extremely trustworthy.
  • House prices in Alton, which is only 25 minutes from London, are soaring.
  • Mathematics, rightly viewed, possesses not only truth but supreme beauty. (Philosopher Bertrand Russell)
When commas are used to offset a parenthesis, it keeps the focus on the surrounding text. As commas play other roles in sentences (e.g., to separate list items and to offset adverbial phrases), readers can sometimes become confused over where a parenthesis starts and ends.

Also, if a parenthesis itself contains a comma or commas, it is advisable to avoid commas to offset it. For example:
  • Dave Bellamy, like his father, Peter Bellamy, last year, was victorious in this year's regional pie-making finals.
  • (This could be confusing.)
  • Dave Bellamy (like his father, Peter Bellamy, last year) was victorious in this year's regional pie-making finals.
  • (This version is clearer.)
Parenthesis Offset with Dashes
  • They roasted the winning brisket — the size of a pillow — in a mighty clay oven.
  • If mankind minus one were of one opinion, then mankind is no more justified in silencing the one than the one — if he had the power — would be justified in silencing mankind. (Philosopher John Stuart Mill)
When dashes are used to offset a parenthesis, it increases the focus on the parenthesis.

Parenthesis in Apposition

"Parenthesis in apposition" is a word(s) used to rename or re-describe a nearby noun (usually the one immediately to its left). Like any parenthesis, it can be removed without damaging the grammatical structure of the sentence. For example (parenthesis in apposition shaded):
  • Peter, my mate from school, won the lottery.
  • (The parenthesis re-describes "Peter," the noun to its left.)
Read more about parenthesis in apposition.

Why Parenthesis Is Important

A text without a single parenthesis would be pretty dull to read. The additional information, aside, clarification, or afterthought provided by a parenthesis in a sentence is usually essential to keep readers informed, engaged, on track, or aligned to the author's thinking. So, writers must be comfortable with using a parenthesis.

Here are three noteworthy points related to parenthesis.

(Point 1) Choose the right parenthetical punctuation.

The prominence of your parenthesis and the flow of your sentence will depend on your choice of parenthetical punctuation. Remember that it is your choice whether to use commas, brackets, or dashes. Here is a summary of the guidelines:


(pro) normal-looking sentence

(con) commas are often confused with other commas in the sentence


(pro) parenthesis easily seen

(con) brackets make official letters look a little unorganized


(pro) parenthesis easily seen

(con) dashes look a little stark

(Point 2) Offset your parenthesis with two parenthetical punctuation marks.

A parenthesis is offset with two parentheses, two commas, or two dashes. If a parenthesis ends a sentence, the second one in the pair is dropped. This is the only time parenthetical punctuation marks do not appear in pairs. It is a common mistake (especially with commas) to use just one.
  • Lee, however has never caught a decent bass. wrong cross
  • (Another comma is required after "however.")
  • Otters – a menace for fish farmers will travel miles in search of a well-stocked lake. wrong cross
  • (Another dash is required after "farmers.")
Read more about parenthetical punctuation.

(Point 3) You don't have to offset a short, obvious parenthesis.

If a parenthesis is short and obvious, it is acceptable to use no parenthetical punctuation. For example:
  • John, however, drinks like a fish. correct tick
  • John however drinks like a fish. correct tick
  • John, on the other hand, drinks like a fish. correct tick
  • John on the other hand drinks like a fish.
  • (We've not marked this wrong, but it is starting to push the bounds of acceptability. If in doubt, use parenthetical punctuation.)

Key Points

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This page was written by Craig Shrives.