What is the of cardinality set?

Answer 1

The cardinality of a finite set is the number of elements in the set. The cardinality of infinite sets is infinity but - if you really want to go into it - reflects a measure of the degree of infiniteness.

So, for example, the cardinality of {1,2,3,4,5} is 5.

The cardinality of integers or of rational numbers is infinity. The cardinality of Irrational Numbers or of all real numbers is also infinity.

So far so good.

But just as you thought it all made sense - including the infinite values - I will tell you that the cardinality of integers and rationals is aleph-null while that of irrationals or reals is a bigger infinity - aleph-one.

Answer 2

The cardinality of a set is the number of elements in the set.