Cardinal numbers
Cardinal numbers (also called whole numbers, natural numbers, or counting numbers) are those used to count physical objects in the real world,
such as
0, 1, 2, 3, 4 .....
They are integers that can be zero or positive.
They assume that the things being counted are not divisible. So we can have 4 cars, but never 3½ cars.
Formally, counting numbers are the set of all nonnegative
integers.
Cardinal numbers are also called counting numbers.
Statistics can confuse you
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.
Cardinality
When we have a set of objects, the cardinality of that set is the number of objects it contains.
See Cardinality.
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Other number topics
Scalar numbers
Counting numbers
Numbers that have factors
Special values
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