Photo of square bracket

When and how to use brackets in your writing

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What is a bracket? Well, apparently it is a coding editor, a type of fungus and, of course, a well-known punctuation mark. Brackets appear in all shapes and sizes, with various different names and uses. During my research my favourite discovery has been some Swedish ones with quills called piggparenteser or ‘mouse parentheses’, which look like a square bracket with little tails.

Origin of brackets

Contrary to popular belief, Erasmus did not invent this punctuation mark, although he did use them and called the round-shaped figure a lunula, as it was like the shape of the moon. The earliest form of any type was a chevron < >. These were first recorded in Cicero’s Episolae Ad Familares (Letters to friends, 62–43BC). Next, the round-shaped bracket appeared in Gapanno Barzizza’s Doctrina Punctandi (1359–1431), a treatise on punctuation. At this time, however, they weren’t called brackets. This word dates to around 1570 in relation to architectural support features; its first use in relation to writing or typography was around 1790. Similarly, the alternative word parenthesis dates to the sixteenth century and is derived from the Greek for ‘a putting in beside’.

Different types of brackets and their uses

On the modern computer keyboard there are four main types of bracket, and the first two (round and square) are those you’re most likely to need in everyday writing. They also have various uses in mathematics, law and computing which I won’t go into here.

( ) Round brackets, also called parentheses
[ ] Square brackets
{ } Curly brackets, also called braces
< > Chevrons, also called angles or carets

Everyday uses

The most common type of bracket you will need to use in your writing is the round bracket or parenthesis. These are always used in pairs. Round brackets are used to separate additional explanatory information in a sentence, to separate abbreviations and for in-text references. The important thing to remember is that the sentence must ‘work’ without the information in brackets, so check whether your sentence still makes sense if the bracketed section is left out. Also, try not to overuse them. Lots of bracketed information in a long sentence can be difficult for the reader to follow.

Square or curly

Square brackets [ ] are mainly used to add comments or corrections into an original text or quotation, for example: “It [the square bracket] can be used to show where text has been omitted using an ellipsis […]” or to identify that the added wording is not in the original quotation. Curly brackets or braces are usually used in mathematics, computing and music. Similarly, you will often come across chevrons or angle brackets in computing, or for dialogue in some translated works. The French are great fans of double chevrons, called guillemets or carets « like these ».


The main convention for punctuating brackets depends on whether the wording within the bracket is a complete sentence. Extra information (like this) does not necessarily need to have any punctuation. If it falls at the end of a sentence, the full stop goes after the second bracket (as here). A complete sentence within brackets should start with a capital letter and end in a full stop inside the final bracket. Similarly: (The extra information within the bracket can also be punctuated with commas, or other marks as appropriate.) If you are using in-text references, like this (Brown, 2016), punctuate as per the citation style you are using, for example, Harvard or APA.

What is nesting?

Too many brackets in normal written text can interrupt the flow when reading so try to use them only when absolutely necessary. Brackets within brackets can be a further problem, best avoided but sometimes it’s just not possible. This is really a style issue, either follow your house style guide or if the choice is yours then be consistent. Oxford style likes round brackets within brackets, like this (round (round again)). I’m not keen on that myself, I prefer to use (round [then square]) as it is easier to distinguish the text, but it’s still not easy on the eye.

The main points to remember are that brackets come in pairs, try not to use too many as it interrupts the flow of reading your writing, and use appropriate punctuation.