Baffled by brackets or puzzled by parentheses?

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Bothered about brackets?

When I first thought about writing a blog post on brackets I didn’t think there would be much to say. After all, brackets are a pretty simple concept right? Well, after a bit of research I soon realised that there might be more to the simple bracket than meets the eye. They come in all shapes and sizes, with various different names, and the different views about punctuating brackets will keep the pedants happy for years. During my research my favourite discovery has been some Swedish brackets with quills called piggparenteser or ‘mouse parentheses’, which look like square bracket with little tails.


The earliest form of a bracket was a chevron < > It is said to appear in Cicero’s Episolae Ad Familares (Letters to friends, 62–43BC). The round shape bracket appeared first in Gapanno Barzizza’s Doctrina Punctandi (1359–1431) – that sounds like a fun read! The word bracket 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’. Wikipedia suggests that Erasmus (1466–1536) called the round-shaped bracket a lunula, referring to the shape of the moon, although he is often wrongly credited with ‘inventing’ the bracket. Although they are often called parenthesis (plural: parentheses) I’m going to stick with the more commonly understood term: bracket.

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 brackets) are those you’re most likely to need in everyday writing. There are also various uses in mathematics, law and computing which I won’t go into here.

Everyday writing

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. As a proofreader, I will always be on the lookout for stray, lonely brackets, and also make sure that pairs of brackets match. Round brackets are used to separate additional explanatory information in a sentence, abbreviations and references. The important thing to remember is that the sentence must ‘work’ without the information in brackets, so check – does your sentence still make sense if the bracketed section is left out?
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 […]”. 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.

Punctuation within brackets

The main convention for punctuating brackets depends on whether the wording within the bracket is a complete sentence. Follow these rules for problem-free punctuation:
A complete sentence within brackets should start with a capital letter and end in a full stop inside the final bracket. (The extra information within the bracket can also be punctuated with commas or other marks as appropriate.)
A phrase or extra information, such as a reference, is punctuated as part of the sentence (Brown, 2016). The full stop is placed after the second bracket.


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.
I hope this brief look at brackets has been useful. 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. If you’d like to learn more there’s some useful information here at OED.