What defines an expression in mathematics?

An expression in mathematics is defined as a combination of numbers, variables, and at least one arithmetic operation (such as addition, subtraction, multiplication, or division). This definition captures the core concept of what an expression is: it does not equate to a value (as in an equation), nor does it make a comparative relationship (as in an inequality).

In contrast, a statement that includes an equals sign refers to an equation, which is fundamentally different because equations assert that two expressions represent the same value. A sentence with multiple variables might suggest complexity in an expression, but it doesn’t necessarily define what an expression is on its own. An inequality compares two expressions but is not considered an expression itself since it indicates a relational statement rather than a singular mathematical structure. Thus, the choice emphasizing a combination of numbers and operations accurately encapsulates the essence of what constitutes a mathematical expression.