Definition:Decimal Expansion/Decimal Point

Definition
Let $x \in \R$ have a decimal expansion:
 * $n. d_1 d_2 d_3 \ldots$

The dot that separates the integer part from the fractional part of $x$ is called the decimal point.

That is, it is the radix point when used specifically for a base $10$ representation.

Also denoted as
The usage of the decimal point varies between the various cultures.

The American system is to use a dot placed on the line:
 * $12.345$

The British system is to place the dot centrally:
 * $12 \cdotp 345$

The European system is to use a comma:
 * $12, \! 345$

Consequently the thousands separator for European numbers is either a dot:
 * $12.345, \! 678$

or a space:
 * $12 \, 345, \! 678$

In the British and American systems can be found for the decimal point, while the European usage of the space is generally used for the thousands separator.