What is the symbol of cardinality of a set?

The symbol for the cardinality of a set is typically denoted by vertical bars surrounding the set, such as |A| for a set A. Cardinality refers to the number of elements in the set, indicating its size. For example, if A = {1, 2, 3}, then |A| = 3. Cardinality can also extend to infinite sets, where different levels of infinity can be represented.