Final answer:
The cardinal number of a set is the count of unique elements in the set.
Step-by-step explanation:
The number of distinct elements in a set is called the cardinal number of the set. It is represented by n(a) or c(a), depending on the notation used.
For example, if a set contains the elements {1, 2, 3, 4, 5}, then the cardinal number of the set is 5.
The cardinal number of a set gives us the count of unique elements in that set.