Square brackets?
I would say the words outside the bracket do need to make a sentence except maybe when used as parentheses within parentheses as described below. Square brackets enclose explanatory or missing material, especially in quoted text. “I appreciate it [the honor], but I must refuse”, for example. Or, “the future of psionics [see definition] is in doubt”. The bracketed expression [sic] is used to indicate errors that are “thus in the original”; a bracketed ellipsis […] is often used to indicate deleted material; bracketed comments indicate when original text has been modified for clarity: “I’d like to thank [several unimportant people] and my parentals [sic] for their love, tolerance […] and assistance [emphasis added]”.[3] Square brackets are used in mathematics in a variety of notations, including standard notations for intervals, commutators, the Lie bracket, and the Iverson bracket. Square brackets are also used as parentheses within parentheses (alternating between parentheses and squar
