Decimals are numbers that we use in math. They show part of a whole number. For example, if you had 2.5, 2 is a whole number, and .5 is a fraction of the number. Decimals are really useful for showing parts of numbers when we count money, measure distances, or measure time. When you see a decimal, the number to the left of the decimal point is a whole number, and the numbers to the right tell you how many parts of the whole number there are.