Its first use was Cantor's "Diagonal Argument" for the Continuum Hypothesis, which states that the value of this property must be a nonnegative integer.
If this property's value cannot be expressed in terms of smaller values for it, as in the case of irregular Mose-Kelly sets or non-well-ordered sets, it is called "inaccessible." For the set containing only itself and the empty set, it is one; its value for the power set of any set with value A is given by 2A. It is usually notated by enclosing a set in flat brackets. Its first use was Cantor's "Diagonal Argument" for the Continuum Hypothesis, which states that the value of this property must be a nonnegative integer. For 10 points identify this property, which for the integers has the value aleph-null and is used to designate the relative sizes of infinite sets.
If this property's value cannot be expressed in terms of smaller values for it, as in the case of irregular Mose-Kelly sets or non-well-ordered sets, it is called "inaccessible."
{Cardinality}