Cardinal Number of a Finite Set
It has been told that, the Cardinal number of a finite set A is the number of distinct elements in the set A, and it is denoted by n(A).
Example– 1)
a) A = { week of a year }
There are 52 weeks in a year.
n(A) = 52 or the cardinal number of the set A = 52
Example-2)
If A = { x, y, z } and B = { p, q, r, s } then n(A) = 3 and n(B) = 4
It is not possible to define the cardinal number of an infinite set, the cardinal number of the empty set φ is zero, as φ has no element, or n(φ) = 0, the cardinal number of a Singleton set is 1. For example, if A = { the present president of USA } then n(A) = 1.