Plural of Parenthesis
“Parenthesis” has the irregular plural “parentheses,” with a corresponding pronunciation change. The plural applies both to inserted parenthetical material and to references to the curved punctuation marks. Use singular “parenthesis” for one and plural “parentheses” for more than one or for the paired marks when the construction calls for the plural.
The plural of “parenthesis” is “parentheses.”
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| one inserted aside / one mark | parenthesis | Singular. |
| more than one / paired marks | parentheses | Plural. |
Quick tests
Plural-choice test
Are you referring to more than one parenthesis or to the paired marks?
If yes: Use “parentheses.”
If no: Use singular “parenthesis.”
Caveat: Writing-style questions about punctuation placement remain separate from this lexical plural task.
Examples
Put the reference in parentheses.
The paired punctuation marks take the plural.
The paragraph contains two long parentheses.
More than one inserted aside uses “parentheses.”
A parenthesis can interrupt the main sentence.
One takes singular “parenthesis.”
Further guidance
Core difference
Use “parentheses” for more than one parenthesis.
Fast Test
Count the relevant items: one is a parenthesis; more than one are parentheses.
Usage Boundary
This page covers the noun’s number pattern, not the broader style rules for when parenthetical punctuation should be used.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- PARENTHESIS | English meaning - Cambridge Dictionary (opens in a new tab)Cambridge University Press · Cambridge records parentheses as the plural of parenthesis for both inserted material and the punctuation marks.
- PARENTHESIS Definition & Meaning - Merriam-Webster (opens in a new tab)Merriam-Webster · Merriam-Webster records plural parentheses and the corresponding pronunciation.