Decimal describes our everyday number system, the one you use for everything from counting cookies to measuring distances. It's called decimal because it's based on the number ten (from the Latin word decem, meaning ten).

In the decimal system, each position in a number is worth ten times more than the position to its right. The number 347 means 3 hundreds, 4 tens, and 7 ones. This system uses ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.

The word decimal also refers to numbers that include a decimal point, like 3.75 or 0.5. The decimal point separates whole numbers from fractional parts. In 3.75, the 3 is a whole number, while the 75 represents seventy-five hundredths. Decimals give us a precise way to express amounts that aren't whole numbers: your height might be 4.8 feet, or a race time might be 12.3 seconds.

Not all cultures throughout history used the decimal system. Ancient Babylonians used base 60 (which is why we have 60 seconds in a minute), and computers use binary, a base-2 system with only 0 and 1. Today, the decimal system is standard worldwide and is used in most everyday situations.