What does the term "parentheses" refer to in mathematical expressions?

In mathematical expressions, the term "parentheses" specifically refers to symbols used for grouping. Parentheses are written as round brackets, ( ). They play a crucial role in determining the order of operations within an expression. For instance, they indicate which calculations should be performed first before applying other operations like addition, subtraction, multiplication, or division.

For example, in the expression (3 \times (2 + 5)), the addition inside the parentheses must be executed before multiplying by 3, leading to a value of 21. This grouping feature is essential for clarifying the intent of the expression and ensuring accurate calculations in more complex equations.

The other options do not accurately define parentheses; squared parts in an equation refer instead to exponents, variables are typically represented by letters or symbols that stand for an unknown value, and equal signs indicate the equality relation between two expressions. Thus, understanding parentheses is fundamental to correctly interpreting and solving mathematical expressions.