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# Number of elements

The number of elements of a finite set $A$ is written as $n(A)$ or $\vert A \vert$. It is also called the cardinality of the set $A$.

$$n(\{A,B,I,L\}) = 4$$

A subset $A$ of a finite set $B$ is finite and has fewer elements than the set $B$. This can be written as $$n(A)\le n(B).$$

A proper subset of a finite set has fewer elements than the original set.