Answered By: Leon Research & Writing Studio Last Updated: Dec 19, 2017 Views: 35482
Square brackets are used around words that are added to a quote. These added words are not part of the original quote.
For instance, you might have a source that says "George Sinclair, Abnes Montague, and Daniel Abrams served on the H.M.S. Gannet from 1879 to 1883". If you wanted to remove the sailors' names from the quote, you could simply say "[They] served on the H.M.S. Gannet from 1879 to 1883".
Brackets can also be used with quotes to explain how you changed the quote from the original source. For example, you might write "Spider webs are 2.5 times stronger [emphasis added] than the average human hair."
Another place brackets can be used is in a reference entry, such as with this entry for a podcast:
American Speech-Language-Hearing Association. (Producer). (2009, August 25). Protecting the hearing of the young [Audio podcast]. Retrieved from http://podcast.asha.org/
For more information, see page 173 of the APA Manual. See this related FAQ post on using square brackets and ellipses.