# 2.1.4 Numbers in Standard Form

In the United States, a number in standard form is separated into groups of three digits using commas. Each of these groups is called a period. So in the last section you will have seen that one hundred fourteen thousand, six hundred sixty was written as 114,660.

Here’s a number that is not written in standard form: 100210120. To re-write this in standard form we start from the right and group the numbers into sets of threes:

• The first period is 120.
• The second period is 210.
• The third period is 100.

Thus, the number is 100,210,120.

Compare how both numbers are written. The version in standard form is much easier to understand, which is why we use this system to write numbers.

You may also find that instead of using commas to separate each period a space is left, for example 345 678 943.  This is the convention in some countries to avoid confusion where commas are used in place of decimal points in numbers.

## Activity: Standard Form

In your math notebook, first identify the periods in the number 345678943 and then write it out in standard form. ### Discussion

Remember to group in sets of threes, starting from the right and moving from the left. Then separate each period using commas. 