- Four 4 is a number, a word or symbol used to designate quantities or, by extension, entities having quantitylike properties. Rational Numbers The simplest numbers are the natural numbers, 1, 2, 3, ..., used in counting; they are also called the whole numbers, positive integers, or positive rational integers. The natural numbers are closed with respect to addition and multiplication; that is, the ...www.waste.org/four.html