A positional numeral system that groups objects by ten and uses the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

We say that the decimal number system is a base 10 numeral system. Reading numbers in the decimal system uses the written form of digits like

*one*,*two*,*three*, etc, but also*ten*,*twenty, thirty*, etc., and then*one hundred*,*one thousand*,*one million*, etc.### Educational Note

- When they are written, the digits of large numbers are separated into groups of three digits: 380 645 321

However, we make an exception when a number only has 4 digits, like 2014. In this case, the space is optional. - The digits of decimal numbers are also separated by blocks of three digits: 45.978 097 809 78 …

We add ellipses when the sequence is unlimited: \(\frac{1}{3}\) = 0.333 333 333 … and \(\frac{1}{8}\) = 0.125. - The word form of a number matches the place value of the digits. For compound numbers between twenty-one and ninety-nine we use a hyphen. For example, 3277 is written as three thousand two hundred seventy-seven.