The *decimal system* uses the base 10 notation system to represent real numbers. A *decimal expansion* is the expression of a number within the decimal system, such as 1, 15, 359, 18.7, and 3.14159. Each number within the system is called a *decimal digit.* (Such decimal notation—or a numbering notation based on decimals—was first used in India around 594.) The *decimal point* is represented by a period placed to the right of a unit’s place in a decimal number. It is interesting to note that a comma is used in continental Europe to denote a decimal point, such as 3,25 (translated as 3.25 as a decimal point), which in this case would logically be called the *decimal comma.*