What is a decimal number?

A number between two whole numbers

When you pay 3.45 euros at the bakery, or when you are 1.62 m tall, you are using decimal numbers. A decimal number is a number written with a decimal point: it allows you to express a value that lies between two whole numbers, for example between 3 and 4.

A decimal number consists of two parts, separated by the decimal point:

• the whole number part, to the left of the decimal point;
• the decimal part, to the right of the decimal point.

Example: in 27.84

Whole number part	Decimal point	Decimal part
27	,	84

The value of each digit

After the decimal point, each position has a specific name:

Position	Name	Example in 27.84
1st digit	tenths	8 tenths
2nd digit	hundredths	4 hundredths
3rd digit	thousandths	(if there is one)

A decimal number can also be viewed as a decimal fraction: 27.84 = 27 + 8/10 + 4/100 = 2784/100.

A common pitfall to avoid

Do not confuse the French comma with the full stop used in some countries or on some calculators (27.84 = 27,84). Also note: 3.5 is not “3 point five tenths and five hundredths”; it is simply 3 units and 5 tenths, i.e. 3 + 5/10.