The symbol "( )" is known as parentheses. They are used in writing to add extra information or clarify a point without interrupting the main flow of the sentence. For example, you might say, "My brother (who lives in New York) is visiting this weekend." Here, the information about where your brother lives is included but doesn't distract from the main idea. Parentheses can also indicate that something is optional or can be omitted. In math, they are used to show which operations should be performed first, like in the expression 2 + (3 × 4). This helps ensure that calculations are done in the correct order.