Integers include the whole numbers (also called positive integers or natural numbers), negative whole numbers (also called negative integers or the negatives of the naturals), and zero. Numbers such as 3/4, 5.993, 6.2, -3.2, and pi (π ; or 3.14 …) are not considered integers. Only integers are used when speaking of odd and even numbers (zero is considered to be an even number; for more about zero, see below).