normally you would use an ordinal number [1] to label individual elements of an infinite set while using a cardinal number [2] to measure the size of the set.
i believe the cardinality of a set of words from a finite alphabet (with more than one member) is equivalent to the cardinality of the real numbers. this means that the cardinality of .* is c.
unfortunately, i don't think that cardinality gets us very far when trying to differentiate the "complexity" of expressions like [ab]* from ([ab]*c[de]*)*[x-z]*. probably some other metric should be used (maybe something like kolmogorov complexity).
i believe the cardinality of a set of words from a finite alphabet (with more than one member) is equivalent to the cardinality of the real numbers. this means that the cardinality of .* is c.
unfortunately, i don't think that cardinality gets us very far when trying to differentiate the "complexity" of expressions like [ab]* from ([ab]*c[de]*)*[x-z]*. probably some other metric should be used (maybe something like kolmogorov complexity).
[1] https://en.wikipedia.org/wiki/Ordinal_number
[2] https://en.wikipedia.org/wiki/Cardinal_number