Have you ever seen those little curved symbols in writing that look like this: ( )? They’re everywhere inside textbooks, casual notes, even in jokes online. They’re called parentheses. But here’s the part that often confuses people: what do you call them when there’s more than one? Is it still parenthesis? Or is it something else?

Don’t worry you’re not alone if this feels tricky. The word “parenthesis” has a special plural form that isn’t obvious at first glance. In this article, we’ll explore what that plural form is, why it looks the way it does, and how to use it in real-life sentences. Along the way, we’ll break everything down into simple, easy-to-follow steps. By the end, you’ll be able to confidently say and use the plural of parenthesis without hesitation.

Let’s get started!

What Does “Parenthesis” Mean?

Before we jump into the plural form, let’s first understand the word itself.

A parenthesis is a punctuation mark. It comes as a pair of curved lines: ( ). These are often used to insert extra information into a sentence without interrupting the main idea.

For example:

• My brother (who just learned to drive) took the car out last night.

Here, the phrase who just learned to drive is inside parentheses. It’s extra information. If we remove it, the sentence still makes sense: My brother took the car out last night.

So, in short:

• Parenthesis = one symbol or one set of curved brackets (like this: ( )).

What Is the Plural of Parenthesis?

Now for the main question: What’s the plural of parenthesis?

The answer is: parentheses (pronounced puh-REN-thuh-seez).

Yes, it’s one of those words that changes form in a way that might feel unusual if English isn’t your first language. Instead of just adding “-s” at the end (like cat → cats), it follows a pattern borrowed from Greek.

So remember:

• Singular: parenthesis
• Plural: parentheses

Why Is the Plural “Parentheses” and Not “Parenthesises”?

Good question! This is where the history of the word comes in.

The word parenthesis comes from Greek. In Greek, many words that end in “-is” change to “-es” in the plural form. English borrowed this word and kept the same pattern. That’s why we don’t say parenthesises. Instead, we say parentheses.

This same rule applies to other words too:

• Hypothesis → Hypotheses
• Analysis → Analyses
• Diagnosis → Diagnoses

Notice the pattern? All of these words change the ending from -is to -es in their plural forms.

Is Parenthesis Singular or Plural?

This is a very common confusion. Let’s clear it up.

• Parenthesis is singular. That means it refers to just one. Example:
  • “I accidentally left out a closing parenthesis in my math problem.”
• Parentheses is plural. That means it refers to more than one. Example:
  • “Make sure your equation has two parentheses around the fraction.”

So, whenever you’re talking about just one, stick with parenthesis. When you’re talking about two or more, use parentheses.

Examples of Parenthesis vs. Parentheses in Sentences

Let’s practice with some examples. Seeing the word in sentences will help lock it in your memory.

Using parenthesis (singular):

1. There is a missing closing parenthesis in this sentence.
2. My teacher explained how to use a parenthesis to add side notes.
3. A single parenthesis without its partner looks incomplete.

Using parentheses (plural):

1. The math equation uses two parentheses to group numbers.
2. I love adding jokes in parentheses when I write texts to my friends.
3. Please check your essay; some of the parentheses are not properly closed.

See the difference? Just like with other singular/plural pairs (like book/books or dog/dogs), parenthesis and parentheses switch depending on number.

How Do Parentheses Work in Writing?

Now that we know the singular and plural, let’s talk briefly about how they’re used.

Parentheses are used to:

• Add extra information:
  • I visited Paris (the capital of France) last summer.
• Clarify details:
  • The recipe needs flour (about two cups).
• Provide examples:
  • Some fruits (like apples, bananas, and grapes) are high in fiber.

When you use more than one set in a sentence, you’ll notice why knowing the plural form parentheses is helpful.

Common Mistakes with the Word Parenthesis

Since this word can be confusing, let’s look at some common mistakes people make:

1. Using “parenthesis” when talking about more than one.
   • ❌ Wrong: “There are three parenthesis in this equation.”
   • ✅ Correct: “There are three parentheses in this equation.”
2. Adding “-s” to make the plural.
   • ❌ Wrong: “Parenthesises are hard to use.”
   • ✅ Correct: “Parentheses are hard to use.”
3. Forgetting that parenthesis refers to the symbol itself, not the words inside.
   • Example: In (Hello), the word “Hello” is inside the parentheses. The curved lines are the actual parentheses.

Parenthesis vs. Brackets: Are They the Same?

Sometimes people mix up the terms. Let’s clear it up.

• Parentheses: ( )
• Brackets: [ ]
• Braces: { }

All of these are different punctuation marks, but they each serve different purposes. So when you say “parentheses,” you mean the round, curved ones.

Fun Facts About Parentheses

Let’s make things more interesting with some extra tidbits:

• The word parenthesis comes from Greek roots: para (meaning “beside”) and en-thesis (meaning “putting in”). So literally, it means “to put in beside.” That makes sense because parentheses let you “put in” extra thoughts!
• In math, parentheses are used for grouping numbers and controlling the order of operations. Example: (2 + 3) × 4 = 20, not 2 + (3 × 4) = 14.
• Parentheses are sometimes called “round brackets,” especially in British English.
• In informal writing, people often use parentheses to add a personal tone or a joke. Example: I finally finished the project (after three cups of coffee).

Quick Recap

We’ve covered a lot, so let’s quickly recap the main points:

• Parenthesis = singular (one symbol).
• Parentheses = plural (two or more symbols).
• The plural form comes from Greek, following the pattern of changing “-is” to “-es.”
• Parentheses are punctuation marks used to insert extra information into sentences.
• Don’t confuse them with brackets [ ] or braces { }.

Conclusion

And there you have it, the mystery of the plural of parenthesis solved! It’s not parenthesises or parenthesis again, but parentheses.

The next time you’re writing, whether it’s a school essay, a math equation, or just a funny text to a friend, you’ll know exactly which word to use. Remember: one is a parenthesis, more than one are parentheses.

Language can sometimes feel tricky, especially when words don’t follow the “just add -s” rule. But once you see the patterns (like analysis/analyses and hypothesis/hypotheses), it all starts to make sense.

So, next time someone asks you, “What’s the plural of parenthesis?” you can smile and say confidently: It’s parentheses!