The plural of parenthesis is parentheses. A parenthesis is one inserted remark or one of the curved punctuation marks, while parentheses normally refers to the pair of marks, ( ), or to more than one parenthetical remark. The spelling changes from -is to -es, and the pronunciation changes as well.
Key Facts at a Glance
- Parenthesis is singular; parentheses is plural.
- One curved mark is a parenthesis; the pair is parentheses.
- Parenthesis is pronounced approximately puh-REN-thuh-sis.
- Parentheses is pronounced approximately puh-REN-thuh-seez.
- Parenthetical material is usually removable without making the main sentence incomplete.
- Periods go outside parentheses when the material is a sentence fragment and inside when the material is a complete standalone sentence.
What Is the Difference Between Parenthesis and Parentheses?
Parenthesis names one item, while parentheses names two or more items or the enclosing pair of curved marks. The singular form can refer to one inserted comment, one opening mark, or one closing mark, depending on context.
| Term | Number | Meaning | Example |
|---|---|---|---|
| parenthesis | Singular | One inserted remark | The final parenthesis adds a date |
| parenthesis | Singular | One curved mark | Type an opening parenthesis |
| parentheses | Plural | More than one remark | The essay contains two parentheses |
| parentheses | Plural | The pair ( ) |
Put the citation in parentheses |
In everyday writing, people usually say a parenthesis for one mark and parentheses for the pair. Technical documentation may distinguish the marks more precisely as the opening parenthesis and closing parenthesis.
The word also has a grammatical meaning. A parenthesis can be a word, phrase, or sentence inserted into another sentence as supplementary information. The punctuation marks are the visible mechanism that encloses that material.
Is Parentheses Singular or Plural?
Parentheses is plural. The singular noun is parenthesis, following the Greek-derived spelling pattern in which singular -is changes to plural -es.
| Singular | Plural | Similar pattern |
|---|---|---|
| parenthesis | parentheses | analysis, analyses |
| thesis | theses | thesis, theses |
| diagnosis | diagnoses | diagnosis, diagnoses |
| hypothesis | hypotheses | hypothesis, hypotheses |
The plural form is not parenthesises in standard English. Although English sometimes regularizes borrowed nouns with an -es ending, parentheses remains the established plural in dictionaries and formal writing.
How Do You Pronounce Parentheses?
Parentheses is commonly pronounced puh-REN-thuh-seez, with the main stress on the second syllable. Parenthesis is pronounced puh-REN-thuh-sis, so the final sound changes from sis to seez.
| Word | Approximate pronunciation | Final sound |
|---|---|---|
| parenthesis | puh-REN-thuh-sis | “sis” |
| parentheses | puh-REN-thuh-seez | “seez” |
| hypothesis | hy-POTH-uh-sis | “sis” |
| hypotheses | hy-POTH-uh-seez | “seez” |
Pronunciation guides use different phonetic systems, so dictionary transcriptions may look different. Merriam-Webster and the Cambridge Dictionary both distinguish the singular ending from the plural ending, even though regional accents alter the unstressed vowels.
A useful speaking test is to say one parenthesis and two parentheses aloud. The plural is not formed only by adding a written ending; the final syllable changes in speech.
When Should You Use Parentheses?
Use parentheses for supplementary information that the reader can remove without losing the main sentence’s grammatical structure. Common uses include brief explanations, dates, acronym definitions, numerical details, translations, citations, and restrained asides.
The removal test is reliable in ordinary prose:
- Correct: The laboratory report
(completed in May)identified two errors. - Without the parenthetical: The laboratory report identified two errors.
The central sentence remains complete. The enclosed date adds useful context but does not supply a subject, verb, or required complement.
Main Functions of Parentheses
| Function | Typical content | Example |
|---|---|---|
| Acronym definition | Full name followed by abbreviation | World Health Organization (WHO) |
| Date or location | Time, place, or background detail | The bridge opened in 1968 (in Bristol) |
| Clarification | Number, translation, or specification | Submit two (2) signed copies |
| Citation | Author, date, page, or source | The result was significant (Lee, 2022) |
| Editorial aside | Limited supplementary comment | The replacement part (finally) arrived |
Parentheses reduce emphasis. A reader sees the main clause first and treats the enclosed material as secondary. That makes parentheses useful for technical specifications, but less suitable when the inserted information carries the central argument.
What Is a Parenthetical Expression?
A parenthetical expression is a removable word group that interrupts or supplements a sentence. Parentheses can enclose it, but commas or em dashes can also mark it.
- Parentheses: The contract
(signed on Friday)becomes active today. - Commas: The contract, signed on Friday, becomes active today.
- Em dashes: The contract, signed on Friday, becomes active today.
The choice changes emphasis rather than basic meaning. Parentheses push the information into the background, commas integrate it into the normal rhythm, and em dashes give it stronger visual prominence.
Where Does the Period Go With Parentheses?
Put the period outside the closing parenthesis when the parenthetical material is only a fragment. Put the period inside the closing parenthesis when the parenthetical material forms a complete standalone sentence.
| Construction | Correct example | Reason |
|---|---|---|
| Fragment inside | The shipment arrived late (after the storm). | Main sentence owns the period |
| Complete sentence inside | The shipment arrived late. (The storm blocked the road.) | Parenthetical sentence owns its period |
| Complete main sentence with internal citation | The shipment arrived late (Jones, 2024). | Citation is not a sentence |
| Question inside | Did the shipment arrive? (The carrier provided no update.) | Each complete sentence has its mark |
A parenthetical fragment does not receive an internal period merely because it appears at the end of the sentence. The period belongs to the larger sentence.
Question marks and exclamation points follow the same logic. Place the mark inside if the parenthetical material is the question or exclamation; place it outside if the whole surrounding sentence has that function.
- She asked whether the shipment had arrived
(after the storm?). - Did the shipment arrive
(despite the storm)?
The second example is a question because the full sentence asks the question, not because the parenthetical phrase does.
Can a Comma Come Before Parentheses?
A comma normally should not appear immediately before an opening parenthesis. If the main sentence requires a comma after the inserted material, place the comma after the closing parenthesis.
- Incorrect: When the manager arrived,
(at 9 a.m.)the meeting began. - Correct: When the manager arrived
(at 9 a.m.), the meeting began.
The opening parenthesis already marks the interruption, so a comma before it usually creates redundant punctuation. The comma after the closing parenthesis belongs to the main sentence structure.
Other punctuation can appear before an opening parenthesis when meaning requires it. A colon may introduce a parenthetical explanation, and a semicolon may separate independent clauses, but writers should confirm that the parenthetical material genuinely belongs there.
- The result was unexpected:
(the control group improved faster). - The first trial failed;
(the second produced usable data).
These constructions are formal and often read better when rewritten as separate sentences.
Do Parentheses Change Subject-Verb Agreement?
Parenthetical words do not normally change the number of the main subject. The verb agrees with the grammatical subject outside the parentheses, unless the inserted wording changes the actual syntactic construction rather than merely adding information.
- Correct: The director
(along with two advisers)is attending. - Correct: The directors
(along with one adviser)are attending.
A common mistake occurs when a plural noun inside parentheses distracts the writer from a singular subject. The phrase along with two advisers does not create a compound subject. By contrast, an unparenthesized phrase joined by and usually does:
- The director and two advisers are attending.
- The director
(and two advisers)is attending only if the parenthetical phrase is genuinely treated as an aside, though rewriting is usually clearer.
The safest editorial practice is to remove the parenthetical material temporarily, identify the main subject, and select the verb from that subject.
Parentheses, Brackets, or Braces: Which Mark Is Correct?
Parentheses ( ) enclose supplementary material, square brackets [ ] usually mark an insertion or alteration inside quoted material, and braces { } commonly group alternatives or mathematical sets. Their meanings vary by discipline, but the three marks are not interchangeable in ordinary prose.
| Mark | Common name | Primary writing use | Technical use |
|---|---|---|---|
( ) |
Parentheses | Asides, citations, definitions | Function arguments, grouping |
[ ] |
Square brackets | Editorial additions to quotations | Arrays, indexing, character classes |
{ } |
Braces or curly brackets | Rare prose grouping | Sets, code blocks, placeholders |
< > |
Angle brackets | Specialized markup | HTML tags, comparison operators |
British style sometimes calls parentheses round brackets, while square brackets may be called brackets. American style commonly uses parentheses for ( ) and brackets for [ ].
Nested punctuation needs a hierarchy. When a parenthetical sentence contains another parenthetical insertion, use square brackets for the inner level:
- Correct: The report
(which cites the earlier study [published in 2019])was revised. - Less readable: The report
(which cites the earlier study (published in 2019))was revised.
Many publishers recommend rewriting instead of nesting. Two short sentences usually impose less cognitive load than three layers of delimiters.
How Are Parentheses Used in Academic Writing?
Academic writers use parentheses mainly for citations, statistical values, abbreviations, dates, and compact explanatory details. Citation systems such as APA, MLA, and Chicago author-date use parentheses differently, so the relevant style guide controls the exact format.
| Style system | Parenthetical example | Typical information |
|---|---|---|
| APA 7 | (Smith, 2021, p. 14) |
Author, year, page |
| MLA 9 | (Smith 14) |
Author and page |
| Chicago author-date | (Smith 2021, 14) |
Author, year, page |
| Statistical reporting | t(28) = 2.41, p = .023 |
Test, degrees of freedom, result |
APA 7 uses parentheses for many in-text citations and statistical values. MLA generally places the author and page number in parentheses without a comma between them. Chicago author-date separates year and page with a comma.
Parentheses also introduce abbreviations after the first full reference:
- National Aeronautics and Space Administration
(NASA)published the data. - NASA published the data in its subsequent report.
The first mention should normally provide the full name. Later mentions can use the abbreviation alone, unless the audience may not recognize it.
How Do Parentheses Work in Mathematics, Programming, and Finance?
Parentheses group values in mathematics, hold arguments in programming, and often mark negative amounts in accounting. Their meaning depends on the notation system, so a reader should not transfer a writing rule directly into code or equations.
| Field | Parenthesis function | Example | Result or meaning |
|---|---|---|---|
| Arithmetic | Force calculation order | (2 + 3) × 5 |
25 |
| Arithmetic | Change logical grouping | 2 + (3 × 5) |
17 |
| Python | Call a function | print("Hi") |
Displays Hi |
| JavaScript | Group a condition | if (x === y) |
Tests equality |
| Accounting | Mark a negative amount | ($5,000) |
Negative $5,000 |
In mathematics, parentheses override normal operator precedence. Without parentheses, multiplication precedes addition in 2 + 3 × 5, producing 17. With (2 + 3) × 5, the grouped addition occurs first, producing 25.
In programming, a missing parenthesis can cause a syntax error or alter how an expression is interpreted. Function calls commonly use parentheses around arguments, while some languages use parentheses for tuples, conditions, pattern grouping, or macro syntax.
Accounting conventions often place negative figures in parentheses rather than using a minus sign. A financial statement should define the convention in its notes if readers could mistake a parenthetical number for an explanatory annotation.
What Are Common Parentheses Mistakes?
The most frequent parentheses errors are missing a closing mark, enclosing essential sentence material, using unnecessary nesting, and placing the final period incorrectly. Each error can usually be fixed by testing the main sentence after temporarily removing the enclosed words.
1. Enclosing an Essential Verb
- Incorrect: The audit
(revealed no)fraud. - Removal test: The audit fraud.
- Better: The audit revealed no fraud
(despite the delay).
Parentheses should not hide words that the sentence needs for grammatical completion.
2. Leaving a Parenthesis Unclosed
- Error: The revised policy `(approved in June applies immediately.
- Correction: The revised policy
(approved in June)applies immediately.
In digital documents, use the editor’s search function for ( and ) and compare the counts. Equal counts do not prove correct nesting, but unequal counts identify a definite problem.
3. Adding a Comma Before the Opening Mark
- Error: The supplier,
(after several calls), agreed to refund the charge. - Better: The supplier
(after several calls)agreed to refund the charge.
The comma after the closing parenthesis may remain only if the main sentence requires it.
4. Overloading a Sentence
A sentence with several parenthetical groups becomes difficult to scan, especially when each group contains dates, abbreviations, and citations. A practical editing rule is to rewrite a sentence containing more than two parenthetical groups unless the document is a form, data record, or technical specification.
5. Nesting Without a Reason
Use square brackets for a necessary inner layer, then reconsider the sentence. Deep nesting creates visual ambiguity and makes citation boundaries harder to identify.
6. Confusing Parentheses With Brackets
A publisher may require (Smith, 2021) for a citation but [sic] for an editorial note inside a quotation. Substituting one delimiter for another can change the editorial meaning.
Should Professional Writers Avoid Parentheses?
Professional writers should use parentheses selectively, not eliminate them entirely. Parentheses efficiently store low-priority technical details, but repeated asides can make a page feel fragmented and can hide information that deserves direct emphasis.
| Audience | Appropriate use | Better alternative when overused |
|---|---|---|
| Academic readers | Citations, statistics, abbreviations | Footnotes or separate explanation |
| Business readers | Dates, regions, short definitions | Short independent sentences |
| Technical readers | Parameters, units, optional values | Tables or code formatting |
| General readers | Brief clarification | Plain sentence or comma |
| Fiction readers | Rare authorial aside | Commas, dialogue, or em dashes |
Parentheses are not good for carrying a central warning, a required instruction, or a long explanation. A safety instruction such as Disconnect power before opening the panel should remain in the main text, not appear as a parenthetical aside.
Accessibility also matters. Screen readers may announce punctuation inconsistently, and dense parentheses interrupt the spoken rhythm of a sentence. For web content, move essential information into ordinary prose and reserve parentheses for short, genuinely secondary details.
An experienced copyeditor’s rule of thumb is simple: if the reader must remember the parenthetical information to act correctly, remove the parentheses and make that information part of the sentence.
What Does Parenthesis Mean Outside Punctuation?
Parenthesis can mean a digression or interruption in a discussion, not only the punctuation mark. In rhetoric and conversation, a parenthesis is an inserted thought that temporarily moves away from the main subject.
- The speaker made a brief parenthesis about the budget.
- The historical parenthesis explains why the policy changed.
The plural remains parentheses in this abstract sense:
- The lecture contained several historical parentheses.
- The editor removed two unnecessary parentheses from the introduction.
In linguistics and grammar, parenthetical is the related adjective. It describes material that interrupts or supplements a sentence:
- parenthetical remark
- parenthetical clause
- parenthetical citation
- parenthetical information
The adjective does not itself indicate number. A singular parenthetical clause and several parenthetical clauses use the same adjective.
FAQ About the Plural of Parenthesis
Is the plural of parenthesis parentheses or parenthesises?
The standard plural is parentheses, not parenthesises. The word follows a Greek-derived pattern in which a singular noun ending in -is changes to -es, as in analysis, analyses and thesis, theses.
What do you call one of the curved marks?
One curved mark is a parenthesis. The left mark is an opening parenthesis, and the right mark is a closing parenthesis. The two marks together are commonly called parentheses or a pair of parentheses.
Is it correct to say a pair of parentheses?
Yes. A pair of parentheses is precise when referring to the opening and closing marks that enclose one passage. The plural parentheses can refer either to the pair or to multiple parenthetical remarks, so the phrase removes possible ambiguity.
Are parentheses called brackets in British English?
British English often calls ( ) round brackets, while American English usually calls them parentheses. In both varieties, [ ] are commonly called square brackets, although regional terminology can vary by publisher and professional field.
Can parentheses contain a complete sentence?
Yes. When parentheses contain a complete standalone sentence, place the sentence’s period inside the closing parenthesis: The route was closed. (Flooding damaged the bridge.) A parenthetical fragment at the end of a larger sentence takes the larger sentence’s period outside.
What is the difference between parenthetical and parentheses?
Parenthetical is an adjective describing inserted or supplementary material. Parentheses is the plural noun for the curved punctuation marks or multiple inserted remarks. For example, parenthetical information may appear inside parentheses.
The Bottom Line
The answer to whats the plural of parenthesis is parentheses. Use parenthesis for one inserted remark or one curved mark, and use parentheses for the pair ( ) or for multiple remarks. In writing, keep parenthetical content supplementary, place periods according to whether the enclosed material is a fragment or complete sentence, and replace dense or essential asides with direct prose.
