A square bracket, also known as a box bracket, is a punctuation mark that appears as a pair of rectangular shapes: [ ]. It is commonly used in writing to enclose additional information, clarifications, or editorial comments within a text. Square brackets help distinguish this information from the main content, making it clear that it is not part of the original material. In academic writing, square brackets are often used to indicate modifications made to quoted material, such as adding context or changing verb tense. They can also be found in programming languages, where they serve various functions, such as defining arrays in languages like Java or Python.