Parentheses or Parenthesis – What’s the Difference?

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Danielle McLeod

Danielle McLeod is a highly qualified secondary English Language Arts Instructor who brings a diverse educational background to her classroom. With degrees in science, English, and literacy, she has worked to create cross-curricular materials to bridge learning gaps and help students focus on effective writing and speech techniques. Currently working as a dual credit technical writing instructor at a Career and Technical Education Center, her curriculum development surrounds student focus on effective communication for future career choices.

Nobody likes to read bland or boring sentences, but luckily there are multiple ways to add details to your material for reader enjoyment.

One of the most popular techniques is the inclusion of parenthetical elements, additional information that allows you to share details with your reader without breaking the flow of sentences. Set within parentheses (a form of punctuation), these words add tone, details, and definitions to your writing.

A parenthesis is part of a parenthetical expression and can denote a singular expression. Confused about what that means? Read on to fully understand the difference between parenthesis and parentheses and how to use them in your writing.

What Are Parentheses?

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Parentheses (also known as round or curved brackets) are a pair of common punctuation marks that work together to separate a parenthetical clause or phrase from the rest of the sentence. Their use offsets non-essential information from the rest of the sentence.

Although the information contained within them provides the reader with details and further information, the sentence is still easy to understand without its use. This punctuation usage is the most substantial separator you can use for an explanation, asides, and numerical detail.

For example:

  • Next Thursday includes yet another interruption to our work day (this is three weeks in a row) that we have to make up in the classroom somehow.
  • I’m leaving early for Thanksgiving (on November 16), so I can visit my family without feeling rushed.
  • The advisory committee meeting went extremely well (despite starting late), and we have some excellent future plans to look forward to.

Some General Rules About Parentheses Use

Parentheses are a popular way to provide information to your reader in informal and formal writing scenarios, but you never want to overuse them. A parenthetical expression added to a page of text is fine, but if you find yourself including them in all of your paragraphs, you should reconsider your sentence structure.

They also need to be properly capitalized and punctuated. Follow these simple rules to ensure you get their use right:

Rule #1

Do not use an initial capitalization or end mark if a declarative sentence or phrase is offset in another sentence.

For example:

  • I need to clean my kitchen (it is such a mess) before my dinner guests show up!

Rule #2

If the sentence is interrupted by an interrogative or exclamatory sentence in parentheses, use an initial capitalization and the end mark within the parentheses.

For example:

  • The building photographers showed up this morning (Does anyone know how long they will be here?) to build a portfolio for the architect.

Rule #3

Use an initial capital and end mark if a complete sentence falls between two independent clauses.

For example:

  • I cannot wait to leave on vacation! (We are going to surprise our family!) I am so glad that I was able to secure time off from work to make this happen.

Rule #4

Punctuation that belongs to the main sentence or is used in a compound sentence follows the closing parenthesis.

For example:

  • I cannot wait until Friday (one day to go); we are driving up to the mountains to go skiing.

What Is a Parenthesis?

The most common definition of parenthesis is its use as the singular form of parentheses: whereas the word “parentheses” denotes the use of two separate “parenthesis.” For example, the parenthetical sentence is enclosed between an opening parenthesis and a closing parenthesis.

An opening parenthesis will look like this “(.” A closing parenthesis will look like this”).”

What Else Does Parenthesis Mean?

The word “parenthesis” can also be used in an alternative manner. Its dictionary definition also includes its use as “an amplifying or explanatory word, phrase, or sentence inserted in a passage from which it is usually set off by punctuation.”

By this definition, a parenthetical expression, or interlude from the regular course of events, can also be called a parenthesis.

For example, in the bulleted sentence below, we refer to the parenthetical expression, “I was worried for nothing!” as a parenthesis.

Or in other words, the following sentence includes the parenthesis, “I was worried for nothing!”

  • The final exam was much easier than expected (I was worried for nothing!), and I passed the class with flying colors.

In this usage, the word “parenthesis” can also define a singular word or expression that interrupts or adds to something. As a synonym, it means a gap, intermission, interruption, or interval and can be used to replace any of these words.

For example:

  • The parenthesis of her sickness delayed her schooling, forcing her into a recovery program so she could graduate on time.

Let’s Review

Parentheses are used to offset non-essential information from the rest of the sentence in a parenthetical expression. The singular form of parentheses is parenthesis, but you can also use parenthesis to describe a word or phrase that creates the interruption in the first place.

Parenthesis replaces words such as intermission or interval (and the like) in this use.