What symbol expresses a mathematical rule?

A mathematical rule is often expressed using symbols such as an equation, inequality, or function notation. For example, the equal sign (=) indicates that two expressions have the same value, while symbols like <, >, ≤, and ≥ denote relationships between values. Additionally, function notation (e.g., f(x)) represents a rule that assigns an output for each input. These symbols allow for concise communication of mathematical concepts and relationships.