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Decimal separator

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A decimal separator is a symbol used in math. It separates the whole part of a number from the fractional part.

Decimal separators
Decimal separators

The whole part stays on the left side of the mark. The fractional part stays on the right side. In math, this is also called a radix point.

DecimalSeparator
DecimalSeparator

This mark is very important for reading numbers correctly. It tells you exactly how much of a whole thing you have. Without it, a number like 9.95 might look like 995.

Different countries use different symbols for this job. In the United States, the standard is a full stop or period.

Interpunct as decimal point in Henderson 1839
Interpunct as decimal point in Henderson 1839

Many other countries use a comma instead. For example, France and Italy often use the comma. Some people even use a raised dot or a small dash. In South Africa, the comma is the standard choice.

MUTCD-CA G11-6
MUTCD-CA G11-6

Even road signs in California once used a different style. They used small numbers placed high up to show parts of a mile.

People have used many ways to show these parts throughout history. In the Middle Ages, mathematicians used a bar over a digit. Arab mathematicians later used a short vertical stroke called a separatrix.

Decimal separators
Decimal separators

The decimal system we use today comes from Indian mathematics. A Persian mathematician named Al-Khwarizmi helped make it popular in the West. In the 1440s, Giovanni Bianchini used decimal points in his math tables. Later, John Napier used a period in his work in 1614.

DecimalSeparator
DecimalSeparator

Rules for these symbols can sometimes be tricky for computers. In 1958, experts had a big argument about this. It almost stopped the creation of a computer language called ALGOL.

Decimal separators
Decimal separators

Today, most computer languages like C, Java, and Python use a dot. This helps computers stay consistent when they work with numbers. Some languages even let programmers use an underscore to make big numbers easier to read. This helps a person see where one million ends and another part begins.

Using separators also helps us read very large numbers quickly. We use digit group separators to break up long strings of numbers.

Thousands separators
Thousands separators

This makes it easier to see how big a number is at a glance. Some people use a space, a comma, or an apostrophe for this. In India, the way they group numbers is quite special and different. It uses groups of two digits instead of three.

Decimal separators
Decimal separators

These small marks help us make sense of a very big world of numbers.

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🖼️ Images & Media (5)
File:Decimal separators.svg
Decimal separators.svg
File:Thousands separators.gif
Thousands separators.gif
File:Interpunct as decimal point in Henderson 1839.png
Interpunct as decimal point in Henderson 1839.png
File:MUTCD-CA G11-6.svg
MUTCD-CA G11-6.svg
File:DecimalSeparator.svg
DecimalSeparator.svg
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