↑
- MAT102 Prep 12

Cardinality

Definition

Cardinality is essentially a way to count the number of elements in a set.

Denoted by:
- ${\begin{cases} n (A) \\ # (A) \\ c a r d (A) \\ | A | \end{cases}$

Through Functions in Math, we know that we can have injectivity, surjectivity and bijectivity.
This means that $f : A \to B$ could be:
- Injective:
  - Everything in the Domain $A$ , maps to $B$ , the Codomain.
- Surjective:
  - Everything in the Codomain $B$ , maps to something in $A$ , the Domain.
- Bijectivity:
  - $f$ is injective and surjective.
When we have bijectivity, it's easy to compare the size of two sets.