Bracket - [ ]

A bracket -- [ ] -- is a tall punctuation mark typically used in matched pairs within text, to set apart or interject other text (similar, but not identical, to braces-- { }). Used unqualified, brackets refer to different types of brackets in different parts of the world and in different contexts.

Bracket basics

Brackets are punctuation marks that are normally used in mirrored pairs for the purpose of editing quotes within texts. The appearance of brackets makes it easier for readers to distinguish the input of an editor from the original words of an author or interview subject in a book, newspaper, or magazine article. 

Due to the unqualified status of the word "bracket," different punctuation marks bear the name throughout the world. In the U.K., parentheses are referred to as brackets; in the U.S., the name applies to the square-end shapes that appear next to the letter P on most keyboards.

Used correctly in a sentence

The distinct purpose of brackets from that of parentheses allows readers to tell editorial modifications apart from in-text citations and parenthetical statements from the author of a given text. As an editorial device, brackets are most often used for the following three purposes: 

Modifying text from another author:

• The instrumentals on Red were superior to those on Larks' Tongues in Aspic and Starless and Bible Black because the bam-bam, cling-clang, King-Kong-on-a-rampage-type cadence was replaced with something that flowed a whole lot better.
• The instrumentals on Red were superior to those on [the two previous albums] because the [thudding] cadence was replaced with something [more fluid].

Adding information to a pre-existing text:

• The Golden Gate Bridge was an engineering marvel for the 1940s that helped bring the Bay Area full circle from the ravages of the big fire.
• The Golden Gate Bridge was an engineering marvel for the 1940s [editor's note: the Golden Gate opened in 1937] that helped bring the Bay Area full circle from the ravages of the big [San Francisco] fire [of 1906].

Modifying third-party quotes for the sake of readability:

• "I thought it was a horrible, rotten, vicious, sickening thing for him to say, but I can't really recall… I fail to recollect, try as I may, what the fallout was like."
• "I thought it was a [terrible] thing for him to say, but I [don't remember] what the fallout was like."

Brackets help explain content and attribution

The following two versions of an interview snippet show the difference that brackets can make. Here, a British rock veteran's semi-coherent recollections of the mid '60s club scene are modified for improved readability:

Unedited – Those were great days to be going down to the clubs in London, where you had the Pretty Things and the Animals and, and… The Beatles were all over the media, but in the clubs it was all about loud guitars and long, you know, greasy hair and all that Chicago blues influence, with the Downliners Sect and Manfred Mann and Jethro Tull; Mick and all of them going wild on stage. The Yardbirds, they were the best of all of them; Jeff and Jimmy, after Eric…

Edited – [The mid '60s was a great time] to be going down to the clubs in London, where you had [bands like] the Pretty Things and the Animals [playing regularly.] The Beatles were all over the media, but in the clubs it was all about [loud, guitar-based music influenced by the Chicago blues, such as the] Downliners Sect and Manfred Mann and Jethro Tull [editor's note: Tull arrived on the scene in early 1968]; Mick [Jagger] and all of them going wild on stage. The Yardbirds, they were the best of all of them; Jeff [Beck] and Jimmy [Page, who joined the band] after Eric [Clapton].