Brackets (also called parentheses) enclose extra information or explanations which interrupt the normal progression of the sentence.
Note:
Full stops, question marks or exclamation marks are usually put outside the brackets (unless the brackets enclose a complete sentence).
Additional Information in Brackets
Additional information is enclosed in brackets if the information is not essential for the understanding of the sentence.
Example: Connor (Amy's boyfriend) bought the tickets.
Note:
Depending on the importance attached to it, additional information can be enclosed in brackets, commas or dashes.
Brackets – not important
Connor (Amy's boyfriend) bought the tickets.
Commas – neutral
Connor, Amy's boyfriend, bought the tickets.
Dashes – emphasised
Connor–Amy's boyfriend–bought the tickets.
see also: → Additional Information in Commas
see also: → Dashes in Summaries and Additional Information
Abbreviations in Brackets
At the first mentioning of an organisation in a newspaper article, both its abbreviation and the spelled-out form are mentioned, one of which is enclosed in brackets.
Example:
He was an active member of the IOC (International Olympic Committee).
He was an active member of the International Olympic Committee (IOC).