Final answer:
The subscript is commonly used in mathematics, physics, and chemistry to denote different values or quantities.
Step-by-step explanation:
In mathematics, the use of a subscript is common in various contexts. However, in this specific question, it seems like the student is asking about the subscript used in physics and chemistry. In physics, the subscript is often used to denote initial and final values of quantities in a motion or a system. For example, subscript 0 represents an initial value, while the absence of a subscript represents a final value. In chemistry, the subscript is used to denote the number of electrons in a particular subshell.