Some authors include 0, so that the natural numbers are {0, 1, 2, 3, …}. Whole numbers: The numbers {0, 1, 2, 3, …}. Integers ( ): Positive and negative counting numbers, as well as zero:{…, -2, -1, 0, 1, 2,…}. Rational numbers ( ): Numbers that can be expressed as a ratio of an integer to a non-zero integer.
