Definition:Cardinal Number

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Definition

Let $S$ be a set.


The cardinal number of $S$ is defined as follows:

$\vert S \vert = \displaystyle \bigcap \left\{ x \in \operatorname{On} : x \sim S \right\}$

where $\operatorname{On}$ is the class of all ordinals.

Compare cardinality.


Also see


Sources