Square Brackets ( [ ] )

Square Brackets are mainly used for indicating that some words have been excluded from a quotation or that words have been added and do not appear in the original quoted text. They are also used for clarifying information in a reference, and for avoiding nested round bracket parentheses.

Missing words from a quotation

• "The parents also had concerns about the cultural knowledge of the staff at their children’s schools, and how this might affect their education. One said:

  Teachers [ ... ] need to learn how to deal with kids of different backgrounds. [ ... ] I suppose they need to further learn all the different cultures. (Adebayo 2023)

  This is ellipsis. The writer has used it in order quote a long piece of text (a block quote) but without including unnecessary material. Sometimes ellipsis is enclosed in round brackets and sometimes only the dots are used. You should consult a style manual (APA, MLA, etc.) in order to decide which style you need in your text.

Added or modified text inside a quotation

• Staggeringly, in 1996 the company’s chief executive, Lee Raymond, referred to “the unproven theory thatquoted text [ fossil fuels ] affect the earth’s climatequoted text”. (Grant 2013)
  
  The original sentence was "Today, however, a multinational effort, under the auspices of the United Nations, is under way to cut the use of fossil fuels, based on the unproven theory that they affect the earth's climate" (Admin2 1996). The pronoun they refers to fossil fuels so the writer has replaced they with the original reference. If you quote text with a pronoun reference to something previously mentioned, you may have to use this technique to restore the reference and make the quotation make sense.
  
  
• “We just don’t have the knowledge and I wouldn’t feel confident,” one teacher said. Another commented:

  It would be useful to do fitness-type CPD [ continuous professional development ] , but we don’t really have the knowledge to share. We all go the gym, but what we can do with the pupils isn’t really clear. (Cox 2023)

  In this case the words inside the square brackets explain the acronym CPD. It's an appositive.
  
  
• “However, the boys told us that opportunities are lacking at school. “School is mostly football and that,” one said. “When I go home I can do weights, it’s just not something we do here [ at school ] ”. (Cox 2023)
  
  The word "here" in the original spoken words could be ambiguous so the writer has clarified this: here means at school. But because this was not in the original words spoken, at school is enclosed in square brackets.

Reference Information

• Philosophy Overdose (Director). (2022, May 11). A. J. Ayer - What has Become of Philosophy? (1978) [ Video ] . https://www.youtube.com/watch?v=bP9znCxhHcQ
  
  Square brackets are used in bibliographic references to indicate sources which are not typical text based sources. For example video (as in this example), social media posts, presentation slides, brochures, fact sheets.

You can see more information about the use of square brackets and other formatting information on this APA Style Guide.