- A decimal point or decimal is a symbol expressed by a “.“
- A number that contains a decimal point is called a decimal number
- Example: 34.57 is a decimal number because it contains a decimal point
- A decimal separates a number into two parts
- Collectively, the digits to the right of the decimal is called the decimal part of the decimal number
- The value of the decimal part of a decimal number is less than 1, or a fraction of 1
- Example: 75 cents (.75) is less than 1 dollar (1.00)
- Like each digit to the left of the decimal, each digit to the right of the decimal has a place value
- A whole number can be expressed as a decimal number with placeholder 0s representing the decimal part
- Example: 25 = 25.00
- Application: Expressing a number in Scientific Notation
The decimal numeral system (also called base-ten positional numeral system, and occasionally called denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral system. The way of denoting numbers in the decimal system is often referred to as decimal notation.
A decimal numeral, or just decimal, or casually decimal number, refers generally to the notation of a number in the decimal numeral system. Decimals may sometimes be identified for containing a decimal separator (for example the "." in 10.00 or 3.14159). "Decimal" may also refer specifically to the digits after the decimal separator, such as in "3.14 is the approximation of π to two decimals".
The numbers that may be represented in the decimal system are the decimal fractions, that is the fractions of the form a/10n, where a is an integer, and n is a non-negative integer.
The decimal system has been extended to infinite decimals, for representing any real number, by using an infinite sequence of digits after the decimal separator (see Decimal representation). In this context, the decimal numerals with a finite number of non–zero places after the decimal separator are sometimes called terminating decimals. A repeating decimal is an infinite decimal that after some place repeats indefinitely the same sequence of digits (for example 5.123144144144144... = 5.123144). An infinite decimal represents a rational number if and only if it is a repeating decimal or has a finite number of nonzero digits.