What does a period mean in math class?

Answer 1

For the United States:

The period, or decimal as it's called in math, means the number is less than a whole number.

Examples:

3.45 means 3 pizzas and 45% of a Pizza.

$199.89 means 199 dollars and 89% of a dollar (89 cents).

In some European countries, the decimal is used as a comma and the comma as a decimal, but just focus on what it means in your math class.