Final answer:
The independent quantity, or independent variable, is the quantity that is intentionally changed or manipulated in an experiment or equation.
Step-by-step explanation:
The independent quantity, also known as the independent variable, is a quantity that is manipulated or changed in an experiment or mathematical equation. It is the variable that is intentionally varied to observe how it affects the dependent quantity or dependent variable. For example, in the equation y = 2x + 3, x is the independent quantity because we can choose different values for x to see the corresponding values of y.