There are several types of brackets:
- parentheses or “round brackets” ( )
- square brackets” or “box brackets” [ ]
- braces or “curly brackets” { }
- “angle brackets” < >
In mathematics (formula, equations, etc.), brackets have a precise {[()]} hierarchy that also relates to how complex orders of operations can be resolved.
In technical/medical writing it is common that a reversed order is adopted when quoting data: ([]) instead of [()] – see:
» Use brackets inside parentheses to create a double enclosure in the text. Avoid parentheses within parentheses, or nested parentheses … Correct: (We also administered the Beck Depression Inventory [BDI; Beck, Steer, & Garbin, 1988], but those results are not reported here.) Incorrect: (We also administered the Beck Depression Inventory (BDI; Beck, Steer, & Garbin, 1988), but those results are not reported here) «
see https://blog.apastyle.org/apastyle/2013/05/punctuation-junction-parentheses-and-brackets.html
» The old typographical convention which I was told years ago by a retired typesetter, is that if one has nested parenthetical expressions, different characters are used for the inner parenthetical than the outer, so the outer expression is parenthesis, the next level of parenthesis is square brackets, and the next set after that is parentheses again, or sometimes curved brackets, so the pattern is ([{}]). I have most often seen two layers of parentheses in religious writing, where a referenced Bible verse will be quoted in full in parentheses, and the citation–chapter, verse, and translation–will follow the quotation in square brackets immediately before the closing parenthesis. «
– see https://english.stackexchange.com/questions/196031/parentheses-inside-parentheses
» This is an issue that commonly arises in academic writing, particularly when inserting additional information about an in-text reference. For example, you have a parenthetical element, such as an in-text reference (e.g., Elite Editing, 2014). Now, you want to add an additional parenthetical element, such as an abbreviation (EE), into the parentheses. Keeping them as they are (identically curved), can lead to confusion about where the elements start and stop. This is called ‘nested parentheses’. One solution is to turn the interior parentheses into square brackets [ ], to distinguish them from the original curved parentheses ( ). «
– see https://www.eliteediting.com.au/parentheses-within-parentheses/