I was asked by a customer of our e-learning Grammar course about how to use brackets in writing. My first quick answer is: don’t, unless you really have to.
They break up sentences (you see). They contain subordinate information, not primary information. I often skip brackets when reading (they immediately signal that the information in them is not the main point).
On the English keyboard today we have 3 types brackets: (); []; and {}.
There are 4 ways to use them.
To clarify meaning
- To put information within a quotation which the speaker did not say but is needed for a clearer meaning:
“I did not understand [how high the debt was].” He said “I did not understand.” And we add [how high the debt was] to clarify what he did not say but we understood him to mean. Note here we use the square brackets.
For abbreviations
- To contain an abbreviation which will be used later:
The leader of the Association of Chief Police Officers (ACPO) said: “ ACPO is concerned at the level of cuts.” Note these are the rounded brackets.
For conversions
- To put in the conversion of a measurement:
AIG has agreed to sell its Alico brand to MetLife for $15.5bn (£9.7bn). Note again the round brackets.
For references
- To put a reference into a more formal type of writing which will refer to a source in a bibliography:
“At the time of the Indian Revolt of 1857, the 4,500 miles of land lines in India helped the British move troops quickly and crush the uprising in a few months.” (Headrick 1981: 158) And the bibliography entry is:
Headrick, Daniel R (1981) The Tools of Empire: Technology and European Imperialism in the 19th Century Oxford, Oxford University Press.
Note again we use rounded brackets.
Apart from these 4 anything in brackets can stop the flow of the writing, whatever type of writing it is. Don’t forget to have an equal pair of brackets. The other type of brackets, {}, can be used to include a list of options. But it is rather old fashioned now.
And the customer enjoyed the Grammar course, he said.