Learn exactly when and how to use parentheses—including punctuation rules, the removability test, and when to choose dashes or commas instead.
Parentheses enclose nonessential information — if you can remove what's inside them and the sentence still makes sense, you're using them correctly. Punctuation goes inside the closing parenthesis only when the entire sentence lives inside them; otherwise, it goes outside. The real choice between parentheses, em dashes, and commas is tonal and structural: work through the three-question flowchart below to make that choice deliberately rather than by habit.
What Parentheses Do in a Sentence
Parentheses enclose supplementary, nonessential information that clarifies or adds context without changing the meaning of the main sentence. Delete everything inside the parentheses, and the sentence should remain grammatically complete and make perfect sense.
That removability test is the foundational rule every major style guide agrees on. Purdue OWL's punctuation overview states it plainly: use parentheses to set off nonessential material — dates, clarifying information, or sources — from a sentence. The key word is nonessential: the parenthetical content supports the sentence without carrying its core meaning.
What kinds of information earn the parenthesis treatment?
- Clarifications and explanations: The treaty was signed in 1648 (ending thirty years of war in Europe).
- Acronyms on first reference: The World Health Organization (WHO) released its findings last Tuesday.
- Dates and birth/death years: Jane Austen (1775–1817) completed six novels in her lifetime.
- Asides and author commentary: The proposal was accepted unanimously (which surprised no one who had read it).
- Numbers or letters in lists: Please submit (1) your CV, (2) a writing sample, and (3) three references.
- Technical labels like time zones: The call begins at 3:00 p.m. (EST).
What all of these share is that they add context without carrying the sentence's core meaning. Remove them, and the sentence survives.
Here's what the removability test doesn't tell you, though: it breaks down in two important cases. First, parenthetical negation — a phrase like "The policy applies to all employees (not contractors)" looks removable, but deleting it changes the operative meaning of the sentence. Second, legal drafting — contract language often places defined terms or limiting conditions in parentheses that are structurally essential to the clause's legal effect, even though the sentence reads grammatically without them. In both cases, the right move is to pull the content out of parentheses and integrate it directly into the sentence so its importance is unambiguous.
One quick terminology note: parenthesis (singular) refers to a single mark — either ( or ) — while parentheses (plural) refers to the pair. A single parenthesis mark used alone is a punctuation error; they must always come in pairs.
Parentheses vs Brackets vs Braces: (), [], {}
These three pairs of marks look related but serve entirely different purposes. Parentheses () enclose the writer's own asides and explanations. Square brackets [] modify quoted material or signal editorial insertions. Curly braces {} rarely appear in prose — they belong to mathematics, programming, and specialized notation.
| Mark | Name | Primary Use in Writing | Example |
|---|---|---|---|
| () | Parentheses (round brackets) | Writer's own asides, clarifications, dates, acronyms, citations | She arrived early (before the doors even opened). |
| [] | Brackets (square brackets) | Editorial insertions in quotations, [sic], translations, corrections | He wrote, "The president [Lincoln] signed the bill." |
| {} | Braces (curly brackets) | Mathematical sets, programming syntax, specialized notation | {1, 2, 3, 4} — a set containing four integers |
The distinction that matters most for writers is between parentheses and brackets. When you quote someone and need to slip in a word that wasn't in the original — to make the quotation grammatically clear, or to identify a pronoun — you use square brackets, not parentheses. Brackets signal: "I, the editor or writer, added this; it was not in the source."
For example: The official report stated, "She [the committee chair] declined to comment on the matter." The square brackets tell readers that "the committee chair" was not in the original quote — the editor added it for clarity.
The other important case for brackets is [sic], the Latin word meaning "thus" or "so." When you reproduce a spelling error or awkward phrase from a source exactly as it appeared, you add [sic] to signal that the mistake was in the original, not yours.
Curly braces almost never appear in standard prose. You might encounter them in formal logic ({x | x > 5}), in coding contexts, or in some mathematical notation — but in an essay, a report, or a news article, you can ignore them entirely.
What about parentheses within parentheses?
Style guides including APA and Chicago specify that when you need a parenthetical inside a parenthetical, the inner pair should be square brackets, not another set of parentheses. So instead of ((like this)), write ([like this]). It's more readable, and it removes the visual ambiguity about which closing mark belongs to which opening mark. The nesting section below covers this in more depth.
Punctuation Inside or Outside Parentheses?
If the parenthetical is part of a larger sentence, all terminal punctuation goes outside the closing parenthesis. If the entire sentence is enclosed in parentheses, the terminal punctuation goes inside. This single rule, applied consistently, resolves almost every punctuation-placement question.
Example 1 — Parenthetical at the end of a sentence:
She submitted the report on Friday (three days before the deadline).
The period falls after the closing parenthesis because the parenthetical is a fragment attached to a larger sentence.
Example 2 — A standalone parenthetical sentence:
She submitted the report early. (Her manager had been asking for it all week.)
The second sentence exists entirely inside parentheses. It gets its own capitalization and its own period — inside the closing mark.
Example 3 — A mid-sentence parenthetical that contains a question:
He finally showed up to the meeting (can you believe it?) twenty minutes late.
The question mark belongs inside the parentheses because the question is internal to the parenthetical. No additional period after "late" is needed — the sentence's own terminal punctuation handles that job.
What about commas near parentheses?
Commas never go before an opening parenthesis. If the sentence structure calls for a comma, it goes after the closing parenthesis. Wrong: "She arrived early, (before the doors opened) and took a seat." Right: "She arrived early (before the doors opened) and took a seat."
Punctuation goes outside the closing parenthesis when the parenthetical is part of a larger sentence — and inside only when an entire sentence is enclosed. Commas always follow the closing parenthesis, never precede the opening one.
Parentheses vs Em Dashes vs Commas
Parentheses, em dashes, and commas can all set off the same interruptive information, but they send different tonal signals. The choice is a genuine stylistic decision — not a mechanical one — and getting it right changes how readers experience the sentence.
The best way to feel this difference is to watch one sentence rewritten three ways:
- With commas: Marcus, who joined the company just six months ago, led the presentation.
- With parentheses: Marcus (who joined the company just six months ago) led the presentation.
- With em dashes: Marcus — who joined the company just six months ago — led the presentation.
All three sentences communicate the same facts. The reader's experience of each is noticeably different.
The comma version is neutral. It presents the tenure information as a natural part of describing Marcus — relevant but unremarkable. Use commas when the aside flows naturally with the sentence's rhythm.
Parentheses quietly background the tenure detail. They imply: "This is context, not the main story." The sentence puts focus firmly on the act of leading the presentation. Reach for parentheses when the aside is genuinely secondary — useful, but not the point.
Em dashes do the opposite. They stop the reader momentarily, creating a beat of emphasis. The tenure detail suddenly feels surprising or significant. Em dashes say, "Pay attention to this." For more on when em dashes are the right call, see our piece on em and en dashes vs hyphens.
When does each choice go wrong?
Commas go wrong when the aside is so long that the main clause gets lost. Em dashes go wrong when overused — the emphasis stops meaning anything. Parentheses go wrong when the information inside is actually essential to understanding the sentence (see the parenthetical negation problem noted earlier), or when they pile up so frequently that the text reads like a series of footnotes. Copy editors flag that pattern for a reason: heavy parenthetical use usually signals weak sentence structure, not rich detail.
Nested Parentheses (and the Bracket Workaround)
Nested parentheses — a parenthetical inside a parenthetical — are generally discouraged in prose because they're hard to read. When nesting is unavoidable, the standard workaround is to use square brackets for the inner layer: (like [this]). Chicago and APA both specify this approach; AP style leans toward rewriting the sentence instead.
True nested parentheses look like this: (She arrived early (before 8 a.m.) and waited in the lobby.) That double-close )) creates visual noise, and readers often have to backtrack to parse which closing parenthesis matches which opening one.
The cleaner solution is the bracket workaround:
(She arrived early [before 8 a.m.] and waited in the lobby.)
APA style endorses this approach for academic writing — when one set of parentheses must fall inside another, use brackets for the inner pair. Chicago style permits brackets inside parentheses and specifies them for citations that require nested references. APA recommends a single set of parentheses with semicolons for multiple citation elements — (Smith, 2020; Jones, 2019) — which elegantly avoids nesting altogether. AP style effectively discourages nesting by recommending that writers restructure any sentence complex enough to require it.
In practice, the AP approach is often the wisest. If you've found yourself needing parentheses inside parentheses in a regular piece of prose, that's a structural problem worth solving at the sentence level. The bracket workaround is genuinely useful in academic and citation-heavy contexts; in general writing, reaching for it is usually a sign to rewrite first.
When nesting is genuinely required — especially in academic writing — use square brackets for the inner layer: (outer [inner] outer). In most prose, a nested parenthetical is a signal to restructure the sentence, not to add another layer of punctuation.
Parentheses in Academic and Legal Writing
Academic and legal writing use parentheses more systematically than general prose does. In academic work, they handle in-text citations, introduce abbreviations, and contain statistical reporting. In legal writing, they define terms on first use, enclose statutory references, and bracket conditions in contracts — though plain-language reform movements in both fields are pushing back against parenthetical overload.
In-text citations are the most frequent academic case. APA style formats them as (Author, Year, p. #): (Williams, 2023, p. 47). For multiple sources in a single citation, APA uses semicolons inside a single pair of parentheses: (Williams, 2023; Chen, 2022). MLA uses a simpler author-page format: (Williams 47). Across all three styles, the citation lives inside its own parentheses at the end of the relevant clause, before the sentence's period.
Abbreviations on first reference follow a standard form: spell out the full term, then put the abbreviation in parentheses immediately after. On every subsequent use, the abbreviation stands alone. Example: The Intergovernmental Panel on Climate Change (IPCC) released its updated projections last spring.
Statistical reporting in scientific writing puts test results, confidence intervals, and p-values in parentheses: "The difference was significant (p = .03, 95% CI [1.2, 4.7])." Notice that even in this technical context, the brackets-inside-parentheses rule applies to the confidence interval.
Legal writing uses parentheses for definitions — "The Contractor (as defined in Section 2.1) shall deliver..." — and for statutory citations: 42 U.S.C. § 1983 (2018). A genuine edge case arises in contract drafting: parenthetical conditions that appear removable by the grammar test are often legally operative. Plain-language initiatives in legal drafting actively push back against this, recommending that any parenthetical whose removal would alter legal meaning be rewritten as a main clause or a numbered sub-provision.
A Decision Flowchart: Dash, Comma, or Parenthesis?
Choosing the right interrupter comes down to three questions about the information you're inserting: Is it essential or optional? Is it emphatic or just contextual? Does it flow naturally as part of the sentence, or does it sit apart? Working through these three questions in order almost always delivers the right answer — and more importantly, gives you a conscious reason for your choice.
| Question | Answer | Likely choice |
|---|---|---|
| Q1: Is the information essential to the sentence's meaning? (Apply the removability test — but watch for parenthetical negation and legal conditions.) | Yes — the sentence breaks without it, or its removal changes the operative meaning | No punctuation pair needed; integrate it directly into the sentence |
| No — the sentence survives and means the same thing without it | Proceed to Q2 | |
| Q2: Is the information emphatic, surprising, or dramatically important? | Yes — you want the reader to pause and notice it | Em dash |
| No — it's useful context, not a dramatic beat | Proceed to Q3 | |
| Q3: Does the information flow naturally as part of the sentence, or does it sit apart? | It flows — the sentence reads smoothly with it in place | Commas |
| It sits apart — it's an aside, a clarification, or a background detail | Parentheses |
Running a real sentence through the test shows how it works in practice.
Sentence to punctuate: "The budget was approved [this happened after three rounds of revision] before the fiscal year ended."
Q1: Is "this happened after three rounds of revision" essential? No — the sentence is complete without it, and removing it doesn't change the operative meaning. Move to Q2.
Q2: Is it emphatic or surprising? Possibly — if the revisions were contentious and you want the reader to feel the difficulty, em dashes work: "The budget was approved — after three rounds of revision — before the fiscal year ended." If the revision history is just useful background, move to Q3.
Q3: Does it flow naturally or sit apart? This doesn't integrate smoothly as a relative clause, so commas would read awkwardly. It's clearly a background aside. Use parentheses: "The budget was approved (after three rounds of revision) before the fiscal year ended."
Notice what the flowchart does that the removability test alone cannot: it distinguishes between three valid options for nonessential information, based on emphasis and sentence rhythm. A piece of information can pass the removability test and still be wrong for parentheses if it's emphatic enough to warrant em dashes, or natural enough to sit between commas.
Common Parentheses Mistakes to Avoid
The most frequent parentheses errors fall into five categories: making the parenthetical essential (including the negation and legal-drafting traps), misplacing punctuation around the closing mark, over-nesting, frequency creep, and dangling marks. Each is fixable once you know what to look for.
Mistake 1: Making the parenthetical essential — including hidden cases. The obvious version is easy to catch: if removing the parenthetical breaks the sentence, the information doesn't belong in parentheses. The harder version is parenthetical negation: "The policy applies to all employees (not contractors)" passes the grammar test but fails the meaning test — removing the aside changes who the policy covers. Similarly, in legal or technical writing, a parenthetical condition that limits or qualifies a main clause is operative, not decorative. In both cases, integrate the content directly into the sentence.
Mistake 2: Punctuation drift. Placing the period inside the closing parenthesis when the parenthetical is part of a larger sentence is one of the most common errors in edited manuscripts. "She submitted the report on time (three days before the deadline.)" is wrong. The period should follow the closing parenthesis: "She submitted the report on time (three days before the deadline)."
Mistake 3: Over-nesting. ((Double parentheses)) are almost always a sign that the sentence needs restructuring. If you find yourself reaching for nested parentheses in general prose, rewrite first; use the bracket workaround only when restructuring genuinely isn't possible.
Mistake 4: Frequency creep. When parentheses appear multiple times per paragraph, they stop functioning as a signal of secondary importance. Every aside feels equally parenthetical, and readers begin skimming past all of them. The fix is to evaluate each set of parentheses individually and ask whether a different construction — a comma, an em dash, or a separate sentence — would carry the aside more clearly.
Mistake 5: The dangling parenthesis. Using ( without a matching ) — or vice versa — is a mechanical error that's easy to introduce during revision when text gets cut and the closing mark disappears with it. A quick scan of any heavily revised passage is worth the time, and an automated pass helps too — our Punctuation Checker catches unmatched marks and the misplaced periods described in Mistake 2.
One broader point: not every parenthetical that survives the removability test should stay in parentheses. If you're parenthetically explaining something the reader already knows, or hedging a claim you should just make directly, the parentheses aren't doing you any favors. Cut them and tighten the sentence. Parentheses used well are invisible; parentheses used defensively just add clutter.
The five most common parentheses mistakes share the same root cause: using parentheses as a convenience rather than a deliberate choice. The removability test is necessary but not sufficient — also check for hidden essentiality (negation, legal conditions), punctuation placement, nesting, and frequency.
Frequently Asked Questions
What are these () called?
They're called parentheses (plural) or, when referring to just one mark, a parenthesis. In some countries, especially outside North America, they're also called round brackets, to distinguish them from square brackets [] and curly brackets {}. In everyday usage, "put it in parentheses" means using both the opening ( and closing ) marks together.
What is the difference between parenthesis and parentheses?
Parenthesis (singular) refers to a single mark — either ( or ) — or to the grammatical construction itself (the aside or interruptive phrase). Parentheses (plural) refers to the pair of marks used together. In practice, writers almost always use the plural form when discussing punctuation: "use parentheses to enclose the date."
What is an example of a parenthesis?
A classic example is: "The film was released in 1994 (the same year as Pulp Fiction) to strong reviews." The phrase inside the parentheses adds context about the year but isn't necessary to understand the sentence — remove it and "The film was released in 1994 to strong reviews" still works perfectly. Other common examples include introducing acronyms (NASA), adding birth and death dates for historical figures, and providing in-text citations in academic writing (Smith, 2020, p. 14).
Should the period go inside or outside the closing parenthesis?
It depends on whether the parenthetical is a standalone sentence or part of a larger one. If it's part of a larger sentence, the period goes outside: "She arrived early (before the doors opened)." If the entire sentence is enclosed in parentheses, the period goes inside: "(She arrived before the doors opened.)" This rule holds for question marks and exclamation points as well.
When does the removability test break down?
In two important situations. First, parenthetical negation: "The rule applies to all staff (not volunteers)" looks removable grammatically, but removing it changes the operative meaning of the sentence — who is covered. Second, legal and technical drafting: conditions or definitions placed in parentheses are often legally or functionally essential even when the surrounding sentence reads grammatically without them. In both cases, the right fix is to pull the content out of parentheses and integrate it as a main clause or explicit qualification.
When should I use em dashes instead of parentheses?
Use em dashes when the interrupting information is emphatic, surprising, or dramatically important — when you want the reader to pause and notice it. Use parentheses when the information is genuinely secondary: a clarification or background detail that supports the sentence without competing with it. The three-question flowchart in the decision section above walks through this choice step by step. Our em dash vs hyphen guide covers the dash side of the decision in more depth.
Can I use parentheses in formal academic writing?
Yes, and they're actually required in many academic styles for citations and abbreviations. APA, MLA, and Chicago all use parentheses for in-text references. That said, most style guides advise limiting parenthetical asides in academic prose — the safer habit is to check whether another punctuation mark would carry the aside more clearly. Use parentheses for citations and first-reference abbreviations freely; use them for commentary and asides sparingly.
Are parentheses used differently in math than in writing?
Completely differently. In mathematics, parentheses control order of operations — expressions inside them are evaluated first, as in (3 + 4) × 2 = 14. This rule has nothing to do with grammar or supplementary information. In writing, parentheses signal that the enclosed content is nonessential to the main sentence. The two uses share the same marks but operate under entirely different systems, so math rules don't carry over to prose and vice versa.
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