A discrete quantity is a quantity that can only take distinct, separate values in an interval. There are no values between these distinct values. The number of students in a class, the number of tickets for a concert, and the number of goals scored in a soccer match are examples of discrete quantities. These values are countable and typically represented by integers or whole numbers. Note that the value of the quantity can only be specific amounts such as $0,$ $1,$ or $2,$ as buying a fraction of the ticket is not an option. Although discrete quantities are often restricted to whole numbers, there are exceptions. Depending on the context, discrete quantities can take values from a set like $\{\text{-}0.8,\text{-}0.4,0,0.4,0.8\}.$ If the independent variable of a function is a discrete quantity, the function is said to have a discrete domain. A function of this type can be identified by its graph, which is composed of any number of unconnected points. Consider the function that models the costs of concert tickets, specifically for $0,$ $1,$ $2,$ $3,$ and $4$ tickets.

The domain of this function is the set of integers from $0$ to $4,$ indicating that the function has a discrete domain.