Cardinal numbers (also called whole numbers, natural numbers, or counting numbers) are those used to count physical objects in the real world, such as
Formally, counting numbers are the set of all non-negative integers.
Cardinal numbers are also called counting numbers.
You may have heard something like "the average household has 1.8 children". Obviously, every family has a whole number of children. The average is found by adding up all the children and dividing by the number of households. Once you do that division you no longer have a cardinal number. That result is a statistic and is actually a real number - one that can have fractional parts.
When we have a set of objects, the cardinality of that set is the number of objects it contains. See Cardinality.