• ### Absolute Value

(Positive) distance between a number and zero on the number line; the corresponding "unsigned" number. | - 4| = 4 and | 4| = 4.

• ### Counting Numbers

Also called natural numbers, the set of positive numbers used to count objects. 1, 2, 3, 4, 5, ...

• ### Integers

The set of numbers including all the whole numbers and their opposites (the positive whole numbers, the negative whole numbers, and zero) -- fractions and decimals are not integers. ... -3, -2, -1, 0, 1, 2, 3, ...

• ### Irrational Numbers

The set including all numbers that are non- terminating, non- repeating decimals.

• ### Natural Numbers

The set of positive numbers used to count objects (also called counting numbers). 1, 2, 3, 4, 5, ...

• ### Negative Numbers

The set of numbers to the left of zero on the number line--numbers less than zero.

• ### Number Line

A horizontal line that has points that correspond to numbers. The points are spaced according to the value of the number they correspond to; in a number line containing only whole numbers or integers, the points are equally spaced.

• ### Opposite

A number that is the same distance from zero as a given number, but on the opposite side of zero. For example, 7 and -7 are opposites, and -9 and 9 are opposites.

• ### Positive Numbers

The set of numbers to the right of zero on the number line--numbers greater than zero.

• ### Rational Numbers

The set of numbers including all the integers, plus all the fractions, or terminating decimals and repeating decimals. Every rational number can be written as a fraction a/b, where a and b are integers.

• ### Real Numbers

The set of all the rational numbers and all the irrational numbers.

• ### Whole Numbers

The set of numbers including all the natural numbers and zero--negative numbers are not whole numbers. 0, 1, 2, 3, 4, ...