Use brackets to enclose any words or phrases that you have inserted into an otherwise word-for-word quotation.
Audubon reports that “if there are not enough young to balance deaths, the end of the species [California condor] is inevitable” (4).
The sentence quoted from the Audubon article did not contain the words California condor (since the context of the full article made clear what species was meant), so the writer needed to add the name in brackets.
The Latin word “sic” in brackets indicates that an error in a quoted sentence appears in the original source.
According to the review, Nelly Furtado’s performance was brilliant, “exceding [sic] the expectations of even her most loyal fans.”
Do not overuse “sic,” however, since calling attention to others’ mistakes can appear snobbish. The preceding quotation, for example, might have been paraphrased instead: According to the review, even Nelly Furtado’s most loyal fans were surprised by the brilliance of her performance.
note: For advice on using “sic” in MLA, APA, and Chicago styles, see 55a, 60a, and 63c, respectively.