Overview
Parentheses ( ) add supplementary, non-essential information to a sentence. Square brackets [ ] are used inside quotations to add or clarify words not in the original. In academic writing, brackets show editorial insertions. The information inside must not be essential to the sentence's meaning.
Parentheses ( )
- Parentheses add supplementary or non-essential information.
- Extra infoThe meeting (originally planned for Monday) was postponed.
- AcronymsThe World Health Organisation (WHO) issued a warning.
- NumbersThree items were missing (pages 4, 7, and 12).
- NoteThe sentence must still make sense without the parentheses.
Square Brackets [ ]
- Square brackets add editorial clarification inside a quotation.
- ClarifyHe said, 'She [the manager] approved the budget.'
- [sic]Used to show an error in the original: 'Their [sic] are three options.'
- Change'[T]he results confirm the hypothesis.' (lowercase → uppercase)
Punctuation Rules
- If the parenthetical is inside a sentence, put the full stop outside: She arrived early (as usual).
- If the parenthetical is a full sentence alone, the full stop goes inside: (She arrived early.)
- Commas go after the closing parenthesis, never before the opening one.
When to use
Academic writing
This phenomenon (known as confirmation bias) affects decision-making.
Journalism
The prime minister (who took office in 2021) made the announcement.
Legal writing
The defendant (hereafter referred to as 'the respondent') appeared in court.
Citations
As Smith [2020] noted, the results were inconclusive.